...the best writing by children and teenagers can be astonishingly poignant, hilarious, and indeed helpful.and they should certainly be enouraged, :
In your early teens, you're not necessarily aware of how derivative your literary outpourings are, and the extent to which your reading shapes your writing; and you may not yet be sufficiently master of your own voice ...One young writer she holds up as an example is Nancy Yi Fan, author of the Swordbird series (with 2 novels under her belt at 15) :
... obviously a very talented teenage writer, but her often infelicitous phrasing ... and the heavy-handedness of her good v evil take on her avian universe suggests that the publisher would have done better to wait for her to mature a little more before rushing her into print.She also mentions Daisy Ashford wrote The Young Visiters when she was just 9 years old in 1919 (when the novel was published many years later, it went through 18 times in its first year alone) and "the most famous piece of published writing by a young author", Anne Frank's Diary of a Young Girl.
(She might also have included Christopher Paolini, author of the Brisingr series who is enjoying a great deal of commercial success.)
But with all these younger writers, you find yourself wondering just how they will judge their earlier work when they do reach maturity. Will it be with great pride or toe-curling embarrassment?
Anyway, if you are a teen who wants to write, you might find this list of books compiled Aaron Shepard useful.