Most Writers Are Adults

""Because never in my entire childhood did I feel like a child. I felt like a person all along--the same person that I am today. ....The nasty side of myself wanted to answer that guidance counselor by saying, the only reason you don't think gifted children talk this way is because they know better than to talk this way in front of you"."

- Orson Scott Card, defending his use of this trope in the introduction to Ender's Game

Toddlers can form complex ideas and speak in full sentences. Eight year-olds are looking for their true love. Your fourteen-year old will often fret about work and already be looking to settle down with their high school sweethearts. A group of nine-year olds will bike on down to the next town with no parents in tow. The seven-year old kid down the street will never eat a bunch of sugar and cry because he didn't get the toy he wanted; he's too busy planning out a zany, very involved scheme to get what he wants.

You may have noticed that children in fiction are... not exactly like their Real Life audience. There's a good reason for this. Any fictional depiction of young people is going to be viewed through the lens of an adult. Most writers aren't themselves children. They tend not to be child psychologists either. If they don't happen to have children, but must write young characters, they tend to end up with characters who are tiny adults. The characters are physically children but they are still treated as adults in most situations (except for when plot calls attention to it). This is usually in terms of personality, how they react to situations, and the situations that they get into in the first place, which tend to involve plot points generally associated with more mature series.

This is significantly more prevalent in animated shows starring kid characters, since it's easier to get an adult voice actor to act like an adult than to get a live action child actor to act like one, naturally. Often a staple of ongoing series that use Adults Are Useless, the Kid Hero, or really anything where kids are the main characters but the series is targeted towards all ages. This is an omnipresent trope. In general, fictional children tend to act at least five years older than their stated age. There is some overlap with Wise Beyond Their Years, but that trope deals with cases where one or two characters act like this.

Part of the problem with writers writing like a child is that their writing sounds childish - which is why this is an omnipresent trope. Also, do not underestimate children; there are pre-adolescents who vaguely understand sexual matters from an intellectual viewpoint, read encyclopedias and other adult literature, and in the past were apprentices in various trades - so they cannot afford to act or speak childishly. Please note that there is an inverse function to this trope - most writers are adults, but are so aware they're writing for children that certain activities will be excised from underage characters even if it's realistic for that age. So your sixteen-year-old won't be dying to get laid; they're searching for true love, and all relationship interactions will be completely romantic rather than sexual (excepting asexual characters). And they'll never smoke, drink, or get high unless it's a Very Special Episode or the character's an antagonist. Also note that children acting in ways that they shouldn't be able to, i.e. like adults, is also a common go-to Horror Trope.

See also Improbable Age and Vague Age. Sometimes results in Menace Decay. Compare Most Writers Are Human.

Anime and Manga

 * In Pokémon ten is the age at which one can leave home to become a Trainer and fend for him- or herself. And while they are still called "boys" and "girls" instead of "kids", they still look, talk, and sound more like teenagers. And how do they make money to support themselves (and their Pokémon) if they're traveling all the time and can't hold a job in any fixed location?
 * The Digimon franchise, where a bunch of kids are thrust into the middle of nowhere and exposed to powerful Mons without any adult supervision whatsoever...
 * This trope is justified, for Digimon Adventure anyway. The kids were ripped out of their reality and placed into the Digital World, and its war, against their will. Digimon Adventure 02 is bit more dodgy, since they come and go at will, but at least it's simply what the kids choose to do, and they know another world is at stake, and they're the only ones capable of saving it.
 * Digimon Tamers is the big aversion of the franchise: the characters generally act much more like children, their adventures in the Digital World have clear emotional consequences as one'd expect from children, and they are supported by adults who are instrumental in taking down the Final Boss.
 * Digimon Frontier and Digimon Xros Wars have the same justification as Adventure, with the caveat that Taiki is slightly more reasonably-aged than the Adventure protagonists. Digimon Savers is the most reasonable: the youngest of the protagonists is fourteen, and they're working for what amounts to a police force.
 * Cardcaptor Sakura has underage characters develop romantic feelings for one another, and of course, talking as if they're older than they are.
 * Even goes so far as to have one of the kids in love with her teacher, and vice versa. But then, considering this is CLAMP...
 * The World of Narue. Kazuto develops romantic feelings for Narue, instead of mere lust... although he does sometimes briefly gets perverted thoughts.
 * A Little Snow Fairy Sugar. Saga and her fellow 11-year-olds. She also has a part-time job, prioritizes a lot more than can be expected of any real kids her age, and acts more as a mother-figure than a sister-figure towards her little cousin.
 * The fairies (at least the younger ones, such as Sugar herself) do act more like children, though. Brownie points for that!
 * Naruto is a strange case because while most of the young characters in it would fit the trope, Naruto himself is as mature as a person his age would really be (initially), making him seem immature just by virtue of being normal.
 * May be justified in this case, seeing as how the fictional society in which they live apparently saddles young people with responsibilities up to and including conducting wars at much younger ages than we consider appropriate in ours. Some characters, like Itachi and Kakashi when they were young and Shikamaru take this to the point of being flat out Wise Beyond Their Years.
 * FLCL lampshades the hell out of this trope, with twelve year olds Naota and Ninamori always trying (and failing) to act like mature adults.
 * Of course, they are arguably more successful at it than the actual adults in the story.
 * Slightly averted in Dennou Coil, with interesting results: The children, acting as children and treating everything as a game, are capable of more in a virtual environment than adults, that act like an adult (save for moderator Tamako and the grandma). When the children find out it wasn't an online game at all, the story becomes Japanese horror.
 * They all still act remarkably mature for 12-year olds. It's only very occasionally that their behaviour reminds us that they aren't adults. In fact, combined with the fact that they sound quite mature as well, the only thing that reminds us that they aren't in their late teens is their modest development.
 * One point of criticism in the Anime News Network review of Magical Girl Lyrical Nanoha is the seemingly unrealistic maturity of the main character. The first time we see the nine-year-old heroine, she's pondering the direction and purpose of her life, which has been perfectly ordinary so far.
 * Very, very averted in everything Hayao Miyazaki ever writes, except the ones that don't actually contain children. Even Markl only acts mature because he's consciously trying to.
 * Lampshaded on Yu-Gi-Oh! GX. Teenagers should not be saving the world!
 * Arguable in Kanon, where 18-year-old Yuichi and others talk kinda like adults... even though just the opposite of this trope is displayed particularly with Ayu.
 * Ayu and Makoto are the biggest exceptions to the trope, for justified reasons. Ayu is mentally younger than she seems, . And Makoto is the youngest member of the cast at around 14 or so....
 * Ditto for just about everyone in The Melancholy of Haruhi Suzumiya, also released by same company Kyoto Animation. That is, except for Haruhi herself and Kyon's ten-year-old sister.
 * Ironically inverted with another K.A. work, Lucky Star, where the "teenage" girls look, talk, and sound like preteens. The cutesy music and pastel-colored artwork only makes this series feel more like elementary school than high school.
 * Until they start talking about eroges. Or about Yaoi. Or about their periods. Yeah.
 * Gundam abuses the hell out of this trope for just about every single series. Many of the Super Prototype Gundam pilots are just an Ordinary High School Student around the age of 16 who's never even touched something of such mechanical complexity, (But are frequently well gifted with robotics) however can instantly grasp how to operate the machine. Even if top Aces much older then them had trouble with them in the past. Beyond that point, they often behave with a maturity and sense of purpose a decade beyond their time, unless they are a Wide-Eyed Idealist. Even then, they can possibly be capable of being the leader of an entire country, or at least a Cool Ship.
 * The titular character of Ojamajo Doremi falls in love more often in one season than other people in their whole life. And she is 8 at the start of the first season.
 * Due to Fridge Logic, Lelouch of Code Geass is a borderline example, being a 17-year-old capable of leading an army and dealing with politics without any (visible) prior experience. Yes, he's The Prince and a genius, yet the show asks the viewers to accept that he's capable of leading La Résistance against the well-trained army of The Empire with experienced military commanders ten (Cornelia, Schneizel) to twenty (Tohdoh) years older than him.
 * Now and Then Here and There. It's justified though.
 * Heavily Averted in Pani Poni Dash!. The whole point is that the main character is eleven years old, has a job as a high school teacher, and yet acts childishly as you'd expect someone her age to (such as shrieking at the top of her lungs or calling her students by distinguishing traits rather than their names).
 * Popotan averts this with Mii, who is very hyperactive and obsessed with Magical Girls and puffy things. Played straight, though, with supporting character Daichi and his classmates. Miyuki is arguable.
 * This is a common criticism of Shugo Chara where the 11-12 year old protagonists act like they're 17.

Comics
"Superboy: "I bet you were born potty-trained, weren't you?""
 * The various Robins have been theoretically in their teens. Outside of awkward romance they have rarely had anything in common with teenagers. Then again, they are being raised by Batman. Lampshaded in an issue of Young Justice:


 * The original New Mutants (oxymoron noted) of X-Men fame had this problem. While the kids didn't act like adults per se, they certainly didn't act like teenagers, superpowers notwithstanding. But then again, they were created by Chris Claremont. Marvel later redeemed themselves with Generation X.
 * Sugar and Spike was about two young babies who were fully aware of their surroundings and capable of semi-rational thought, but spoke a language only the two of them understood. "Fxlbgl?" "Rtmskt." "Word."
 * Runaways focuses on a group of preteens and teenagers living together without any kind of adult supervision. For every example of the characters acting their age--making out in public places, not knowing about current events because they've been watching Friends reruns instead of the news--there's a dozen examples of them handling situations your average adult would find overwhelming. And while most of them go through crushes like any normal teenager, two of their relationships become quite serious: Gert and Chase act more like husband and wife than boyfriend and girlfriend, and Xavin and Karolina are actually engaged. (Granted, it started out as an arranged marriage to end the war between their home planets, but they stayed together long after that arrangement fell through.)
 * The Young Avengers are like a less extreme version of the Runaways. All of them are at least living with some sort of adult guardian, but they're still a group of teenagers who banded together to fight crime all on their own.
 * The Legion of Super-Heroes, depending on the version, had characters considered legally adult at 14. The reboot had Ultra Boy and Phantom Girl getting married at some vague age not too long after that, which on top of that happened when another 14 year old almost got married.
 * Inverted HARD with Bio Apocalypse, which was actually written by a child. Your Mileage May Vary on whether the adults actually act like adults.

Film

 * Spy Kids, particularly the sequels and especially the third one.
 * The "kids" in The Wizard talk more like 1980s businessmen. That's not even getting into the pedophilia implications of one scene.
 * "He touched my breast!"
 * "I touched her breast? She doesn't have breasts!"
 * Averted in Paranoid Park, where teenagers actually act like real teenagers, complete with sexuality and the thrill of taking risks. Needless to say, the MPAA classified this as a quite adult film.
 * Inverted in the 2009 Astro Boy movie; most child characters look and behave much younger than their given age. (Astro/Toby is said to be thirteen and more closely resembles a nine-year-old; Cora is claimed to be seventeen but comes off as perhaps fifteen; the twins are said to be nine but seem more like six or seven-year-olds. Zane, on the other hand, is fourteen and seems accurate.) Of course, this is long-term in Astro Boy - the original was claimed to be nine and looks six.
 * According to Siskel and Ebert, this was the main problem with Blank Check: having received a million dollars in cash, the 12-year-old protagonist then proceeds to use most of it on things an adult would want (like black-tie parties and dates with adult women at fancy restaurants), rather than a kid.

Literature

 * Lampshaded in The School Story, a book about a kid who writes a book. One of the adults mentioned that the author seems to be really good at portraying kids accurately.
 * In The Pendragon Adventure, the "books" are Bobby Pendragon's memories of what just happened to him being recorded. He writes in very professional prose.
 * During the course of the series, the timeline is different for him than for the characters who primarily stay on earth; he is probably older than expected (and he does write a lot).
 * A Song of Ice and Fire. Justified though, childhood can be eroded in harsh conditions, and one wouldn't be able to act like a dumb kid in this Crapsack World. For Sansa, who tries to be a good little girl and believes what adults tell her, things do not turn out well.
 * The Baby Sitters Club. It seems that any time they actually ACT like typical 11 or 13 year olds Stacey would find them quite immature. Of course thinking you're SO much more mature than everyone else is also typical 13 year old behavior as well.
 * Also, some of their sitting charges as well (when they're not acting a lot younger than they should be, such as five-year-old Andrew who doesn't know what New Year's is). Take for instance one of the Perkins girls: she's two years old, and yet speaks in complex full sentences and acts more like she's around TEN!
 * And then there were the jobs they were entrusted with by adults, the most Egregious being the "Super Special" plots, where they would take charge of younger kids away from home, including while stranded in a snowstorm and on vacation in New York (which was a strange city to most of them!). All they had to do was offer to help and explain that they had started an after-school baby-sitting business, whereupon one of the parents they'd worked for would chime in with, "They're very responsible," and bingo, they were treated like honorary adults, no further questions asked. And since eleven was the magic gateway to the Competence Zone, often they would be "taking care of" kids who were only a year or two younger, who might exhibit different kinds of brattiness or stubbornness but would always treat them as an authority figure to be strategically undermined instead of just saying, "Dude, you're my age. Stop acting like a camp counselor. No, I don't want to see what's in your Kid Kit." Apparently you can be "handled" up through the age of ten, and after that you enter a higher plane of thinking and gain all kinds of insight into the minds of "kids."
 * Mallory wears an "I <3 Kids" shirt at the age of eleven. If you saw that in real life, you'd assume it was a last-resort item belonging to her mother and they were behind on laundry at her house,
 * Ender's Game. The author does point this out in the foreword of some editions, in what amounts to, "So what?" Somewhat justified by the fact that the kids are supposed to be towering geniuses, and most of them are being pushed to their limits. Especially Ender.
 * Gifted kids love this book and empathize strongly with Ender. May be a case of Reality Is Unrealistic.
 * Averted by the early works of Gordon Korman. He had his first book published when he was 14, and got into a groove of writing stories about kids that feel genuine in tone (if outlandish in narrative events). Although he's grown up by now, works like No More Dead Dogs still feel like they're written by a teenager who happens to be a professional writer.
 * An American Dream. Steven Rojack's stepdaughter Deirdre is fluent in French, has a flair for poetry, has an eloquent understanding of marriage dynamics, and apparently believes that "people want to make love after a death". Rojack openly acknowledges this by noting that "she always spoke like an adult".
 * Averted very much so by authors Beverly Cleary and Judy Blume, in different ways. Beverly Cleary's books about kids have kids who act their age and even do a great job of making you see the way a third-grader (or first-, or fourth-) thinks and views the world, and are very cute and light-hearted. Judy Blume's books are harsher and more towards the cynical scale of the Sliding Scale of Cynicism Versus Idealism, portraying kids who are not only not "innocent", but featuring very harsh realities (middle schoolers who drink, bullies who do not get their comeuppance).
 * To Kill a Mockingbird has been accused of using the "cute precocious kid" device to get away with having six-/seven-/eight-year-old Scout know and think things she really probably wouldn't, no matter how smart she was and how much Atticus told her about practicing law. And then there's Dill's philosophizing; you could argue that he's not really supposed to understand the full reach of some of the things he says, but a lot of the time he just sounds a little too knowing. On the other hand, Scout is supposed to be recalling the plot rather than describing it as it happens, so some at least of the precociousness can be explained by her either "tidying up" what was said or thought through the lens of a rational adult, or simply wrongly attributing stuff in hindsight.
 * Tamora Pierce. Most of her protagonists start out at around ten and grow into their late teens or adulthood, and all the way through they think the same, act the same and talk the same. The Circle of Magic books, for example, feature a Four-Temperament Ensemble who all become accredited mages at the Improbable Age of fourteen and thereafter mix (apparently exclusively) in adult circles, and most any character who even suggests they might not be as mature, capable or knowledgeable as older people is either a Jerkass to be publicly humiliated, a villain to be defeated, or both.
 * Not quite the same. They each go through a lot of Character Development, and all of them have more empathy and self-control and less tendency to whine in later books compared to former ones.
 * In the Tortall Universe, pages start combat training at about ten years old and train for four years to become squires. The two quartets to have much to do with that are told from the POV of a page; the first one, Alanna, acts considerably more childishly than the second one, Keladry. This is probably due to temperament; Alanna is an impulsive hothead, especially in her youth. Still, they tend to be quite mature.
 * Also, Keladry had already witnessed battle on more than one occasion, which is why she wanted to be a knight.
 * Some readers have suggested Tiffany Aching, the nine-year-old witch in The Wee Free Men doesn't seem like a real nine-year-old (she seems to pretty much run the dairy herself, for a start). The Brownie troupe that made Terry Pratchett an honourary member disagreed, though...
 * Averted in Stephen King's IT. King really gets the way children think and reason.
 * Averted in the works of Robert Cormier. His teens swear, masturbate, drink, fight, and just generally flout the artificial limits imposed in the majority of American literature.
 * Scott Ciencin's Dinoverse features a batch of 13-year-olds who sometimes do act their age. They're remarkably composed about the situation they find themselves in - cast back in time by 64 million years and possessing the bodies of large, charismatic Cretaceous-period animals - but they're each variably impulsive, self-centered, grudgy, and kind of whiny. Cue character development; they act much older at the end of the book.
 * Arguably justifiable - most adults would probably find being sent 64my back in time and being turned into dinosaurs to be truely disturbing. Most 13-year-olds would probably find it truly AWESOME.
 * The protagonists in V. C. Andrews works start out as sixteen (sometimes younger), and right from the start, they all act, talk, and think more like thirty-somethings. In the "Orphans" series, the girls are twelve in their individual stories, but act sixteen. It goes the other way around too--notably in Midnight Whispers, where the protagonist's nine-year-old brother acts/is treated more like he's five.
 * Five-year-old twins in the mystery novel Aunt Dimity: Vampire Hunter are able to draw such compelling and detailed pictures of the "vampire" they saw in the woods that it nearly gives their mother nightmares. Most kindergarteners still draw "people" as a circle with sticks coming out of the bottom for legs.
 * In A Series of Unfortunate Events, Sunny Baudelaire is a baby, yet has the same knowledge and intelligence as her teenage siblings, and this is not treated as remarkable.
 * Ayla in Clan of the Cave Bear matures exeptionally fast both physically and emotionally. She is taught to become a medicine woman at the age of six, teaches herself to hunt at the age of nine (which was also when she has her first death curse, the neanderthal equivelent of incarceration), goes through sexual maturity at the age of ten and has her first child at the age of eleven (!!!). Then again, she is raised by neanderthals, who physically mature at a faster rate than the cromagnons and wonder why she did not physically mature EARLIER than she did.

Live Action Television

 * Most teen soaps in general, especially those with Dawson Casting:
 * The OC
 * Saved by the Bell, too. The characters on that show act more like 20/30-somethings than teenagers. Ironically, despite averting Dawson Casting, they also look more like 20-somethings than teenagers.
 * Quite a few of Hispanic Soap Operas directed to kids and tweens have an over-emphasis on romantic plots. This has come to bite back, since Real Life preteens now seem as worried about romantic issues who are seen by their parents as way over their age.
 * In Carrusel, the girls play with dolls and read comic books, while at the same time talking about boys, clothes, celebrity gossip, and romance novels/soap operas. The boys have varying levels of interest in girls, but all still like boyish pastimes.

Newspaper Comics

 * Peanuts. These kids occasionally take on amazingly adult responsibilities, such as the time Charlie Brown checked himself into the hospital.
 * Calvin and Hobbes played this to excellent effect, with him sometimes wise beyond his years, and sometimes just being hyper-articulate about his various selfish whims. To quote Watterson, "Calvin has never been a literal six-year-old."
 * Simultaneously justified and averted in FoxTrot: the featured pre-teens are Jason and Marcus, whose adult speech and mannerisms are justified by them being a pair of hyper-intelligent ultra-nerds. Averted in that the two also indulge in childish mannerisms, and their peers behave in age-appropriate manners.
 * Most of the point of Cul De Sac, similarly to Calvin and Hobbes, is taking children and seeing what happens if they're as articulate as adults while retaining their childish personalities.
 * Bloom County features "children" who work for newspapers, run political campaigns, and hack into government organizations. Granted, this IS a strip with talking animals, space aliens, and tons of breaking the fourth wall so it may be justified as Rule of Funny.

Painting

 * Most artwork from the 16th through early 19th centuries tends to portray children as small adults.
 * Possibly because children wore the same clothes as adults once they got out of baby clothes. Until well into the 19th century, the only difference between a nine-year-old's clothes and a thirty-year-old's was the size.

Video Games

 * Psychonauts, sort of. The characters are all probably between 8 and 12, and they still have relationships, unrequited love, etc. But at the same time, they still have the songwriting skills of young kids, think friendship bracelets are awfully important, and have the general maturity of that age group, such as one camper assuming that his father hates him and wants him to die just because the father is very strict.
 * The majority of the Sonic the Hedgehog cast are under 20, while the main protagonist himself is 15. Tails is 8. Child Genius or not, he seems more mature/rational than the rest of the main cast. Also, since when is a 15 year-old and an 8 year-old allowed in a casino?
 * Backyard Sports.
 * The average age of the cast of The Legend of Zelda the Wind Waker is a lot lower than that of most other Zelda games. You wouldn't notice if it wasn't for them being modelled in Chibi-style. Medli is just as sage-y as every other sage in the series (while being about 10 years younger than every other sage in the series), the Koroks (who are repeatedly called "child-like") speak in a way you would exspect from the royal court members of England and 12 years old Tetra... Let's not start about Tetra.
 * Though the Koroks are child-like because they are the future forms of the also "child-like" Kokiri.

Webcomics

 * inverted in Axe Cop, which actually is written by a child (though edited by his adult brother). This means the adult characters act very much like children.
 * Strangely enough, this is averted in American Nerd in that while the main character lives in an apartment in Japan, alone, Artist is only (right now) slightly older.

Web Original

 * This is a common criticism of the Whateley Universe, which features characters in their mid-to-late teens acting like full-grown adults. The series would make a lot more sense if it was set in a college rather than a high school.
 * And then you have the witches, three characters who are presently in middle school, who come up with childishly simpleminded schemes while spouting babytalk. Their odd, stylistically low maturity level can be very jarring when compared to the behavior of real middle schoolers.

Western Animation
"Katara: I haven't done this [penguin sledding] since I was a kid!
 * Rugrats is the extreme version of this trope, with 2-year olds that acted like 7 year olds that talked in a language incomprehensible to adults. Even moreso Angelica acted much older than three and was treated likewise by the adults.
 * This one was mocked in a Fairly Odd Parents movie, where Timmy Turner enters a show which looks the same, but with the children actually acting like the toddlers they are.
 * In All Grown Up, the kids are 9-13 years old but they all act like they're about 16. Even more ridiculous is that they all seemed to be high schoolers.
 * As time went on, Jimmy Neutron slowly started to treat their main characters more like young adults than eleven year old kids, except for when they needed to either for plot reasons or to set up a gag. This is most obvious in the episode "Stranded," which uses every UST Trope in the book for Jimmy and Cindy.
 * All over the place in Avatar: The Last Airbender. With all the Love Tropes, Drama Tropes, War Tropes, etc, it's not hard to forget that none of the main characters (bar the Big Bad and a few mentors) are older than 16, and neither characters nor the plot are held back by their lack of age; the series mixes adult tropes and Coming of Age tropes, and mixes them very well. Generally, though, it's still a series about two 12-year-olds, a 14-year-old, a 15-year-old, and a 16-year-old who act more like 16-year-olds and two 18-year-olds. Most of the time it's rather tame, but when you consider how young Aang is and how much UST he has with Katara... well, it's rather squicky. Most of the other characters avoid this to an extent by being at around high school age, but still, the canon pairings are implied to be Twue Wuv. This tropes is sometimes owed to Values Dissonance (16 is the marrying age in some cultures in their world, as it was in ours around the same technological age) and Lampshaded tragedy. These kids should be able to act more like kids, but that's one of the down sides of war.

Aang: You still are a kid!"

"Grandpa Phil: For a nine-year-old, you sure like to take the weight of the world on your shoulders."
 * Or maybe the fact that 14-year-old Azula has a criminal record which would make eyebrows raise in Nuremberg tribunal is even squickier than kisses between a 14-year-old and a 12-year-old.
 * Hey Arnold, where the characters are supposed to be in fourth grade, yet no one finds it odd that Arnold's coach asks him to be the best man at his wedding. Or that the main character takes it upon himself to personally fix the problems of every adult in the neighborhood, ranging from a coach's alienation with his Ambiguously Gay son, to paranoia, to illiteracy, to obsessive compulsive disorder, to so many more.

"Adult: Aren't you too young to be doing this?
 * Home Movies, played to great effect though.
 * The South Park kids have gotten more and more adult as time has gone by, for definitions of "adult" that fit within South Park.
 * The Weekenders, which had a bunch of preteens that acted like, and talked like 16-year olds.
 * This was the whole point of Fillmore!, which was basically Law and Order or NYPD Blue set in a middle-school hall monitor department, where all of the child cast and characters acted and treated situations like graffiti and candy eating with the same wordplay, attitude, and gravitas 30-year old beat cops would use in rape and drug cases. What Do You Mean It's Not Awesome? is commonplace to say the least.
 * Doug, a show that took place in middle school where all the kids looked and acted like high school students.
 * Used frequently on The Simpsons. Was lampshaded and justified in one episode where Marge worries that Bart and Lisa (who are 10 and 8 years old, respectively) are already acting like teenagers. Homer chalks it up to all the growth hormones in food.
 * Arthur. Watching a group of supposedly eight and nine year olds (Arthur and his group are stated to be in the third grade, with the occasional fourth-grader) biking around a city, holding jobs, and doing things that are generally more suited for early teens doesn't really make sense. Particularly all those scenes in the Sugar Bowl without a parent in sight... and not to mention the school. Lockers and many-page reports for third graders? Seems more like a junior high than an elementary school, really. Considering Ratburn, though, he just might assign rather difficult work for third graders. One throwaway line was something like, "For today's test, identify every country on this map of the world. And as always, spelling counts."
 * Subverted and played straight on Phineas and Ferb; the main characters clearly have a genius intelligence well beyond most adults, but use their abilities for childish antics like building a roller coaster in their backyard; while there are love interests, these are played more as kiddy crushes than epic romances. A straighter example, or possibly a parody, would be Candace, who at sixteen has already planned out what she wants to name the kids she plans to one day have with her love interest. But even she comes off more as an annoying older sister than an adult most of the time.
 * Candace's behaviour is actually pretty normal for her age. It's pretty common for 16-year-olds to dream of getting married to their crush and a lot of teens have names picked out for future children. I'd say the Trope is averted with her (in addition to busting her brothers, she worries about getting her license, appearing more "mature" to the adults, having a job, and other common teen concerns).

Phineas: Why, yes. Yes, I am."


 * Justified in Kim Possible, as Kim's twin brothers are kid geniuses from a genius family. And like real child prodigies, they do kid stuff and get in trouble, just in an extra-smart way--like unscrewing cables in a jet to see what they do.
 * Codename: Kids Next Door often fell into this, which just got silly when you considered this meant they acted like the adults they hated. One of the ten-year-olds was even in a serious relationship.
 * Powerpuff Girls. Blossom, Buttercup, and Bubbles are supposed to be five years old, yet they (especially Blossom and Buttercup) act like they're at least 12 years old or so, what with their understanding of certain sexual things like seduction, in a mild way at least; the first time they beat the Rowdyruff Boys by kissing them, they were tipped off to that weakness by Miss Bellum hinting at them by telling them to "act nice" and and showing them her cleavage to solidify the fact. True, they aren't necessarily human so that may be a justification on their maturity, but the thing is, it's not just them- most of the other kids in the show are shown to be as equally mature as the Power Puffs. Interestingly, this is also a rather strange case because they still occasionally struggle with problems a five year old might actually have, such as learning manners, getting over "cooties", sharing, and leaning what's right from wrong; but, even then, they learn about those things in a more mature way than actual five year old girls would.