Adding a link to the thread on book recommendations for "free reading" at school, which mentions a 6-year-old.

Adding a link to the thread on American Library Association booklists, which contains booklists for various ages.

Adding a link to the thread Fiction Book recommendations for kid, which inquires about fiction books for an 8-year old who typically reads for information.

Adding a link to an old thread what book your kid is reading this week (2011).