I recently discovered the Stories for Children Magazine at http://storiesforchildrenmagazine.org/ . A monthly e-zine for children ages 3 to 12. This e-zine offers a rich opportunity for children's writers of fiction, poetry, puzzles, crafts, recipes, art work, you name it, including an educator's page for the month's published works.
In addition to accepting submissions from adult writers for children, Stories for Children accepts submissions from young writers under 17 years of age. At present, it isn't a paying magazine, but it's a great opportunity for any writer to begin or to continue building a portfolio of published work, while bringing pleasure to young readers.
If you've already published a book, you can also send them a review copy. If accepted, they will review it, pass on the review to Amazon or Barnes & Noble (if the book is available from either of those sites), post the review in the magazine, give you permission to use parts of the review in your own marketing, and donate the book to a library of the reviewer's choice.
Check this wonderful ezine out at: http://storiesforchildrenmagazine.org/ . You won't be sorry!