Later on, he gets all sorts of speeches about how he should just act like a normal kid and stop worrying about everything.
If a Child Prodigy acts like an adult in a child's world, rather than being thrust into the adult one, they're Acting Your Intellectual Age.
Take this dialogue from the very first episode.Once More With Feeling : After traveling to the past, Shinji looks (naturally) like a teenager.Web Original Deena in The Guild seems much more mature than her older brother.Every season of Digimon has one of these even Digimon Frontier 's Bokomon, who is the level named "child" in Japanese and who speaks and acts like a graduate student dating violence and sexual assault specializing in Digital asian sex dating services World Mythology.Being orphaned at young age and carrying half of the Triforce of Wisdom around with her might have something to do with.Cecil Holmes, Tyler's best friend, falls into this trope as well.The main cast of Animorphs, especially Jake.Frequently speaks in, little Professor Dialog.Except for not hitting puberty yet, of course.The Dresden Files : The Archive is the ultimate example of this trope.Later, when she discovers her powers, she almost immediately takes a responsible view of them akin to Spider Man, except her wakeup call was property damage rather than the death of a loved one.Note that this is based on the mentality of the character.However, some of these characters are simply like this by nature.
Due to some trickery on Tyler's part and some help from the Revenant, he actually becomes a federal agent, and proves to be more professional and competent than most of the adults in similar positions.

Deconstructed, however, in that she is still naive enough to be vulnerable, and her lack of innocence as a child leads to an apparently joyless and lonely adulthood.Though they deal with the knowledge in opposite ways (despite being roommates).Also of note is Leif Faris Klaus.Murasaki in Kure-nai yo-yos between believably childish behavior for her age of 7 and extremely adult-like decision making, especially near the ending of the series.Avatar The Last Airbender : Azula may be considered too old to count, until you recall she managed to organize a coup in a hostile city with her words alone, breaking the Evil Chancellor in the process, at age fourteen.Judas Priest, children who are more mature than their age implies, with a solid comprehension of abstract concepts, good foresight and an understanding of human nature beyond what most kids their age have.One might assume that she wears her maturity so tightly, because the child can't handle that pain.Chiyo-chan from Azumanga Daioh can not only handle high school-level schoolwork, she also manages to be a class rep and hold down a part-time job, and is generally just as mature and capable as her teenaged friends.In Discworld, one of Susan's young charges is six, but according to Susan "in cynicism, she's about thirty-five".

Might have something to do with her destiny to assist the main character, but still.
Child Lucy in Elfen Lied.
Eliot from Space Vulture is an excellent example.