We had this problem in sixth grade. My daughter's Lexile score was so high that there were no books in the school library she could read. They had a rule that they had to read in their Lexile level. Even the books in the town library were unacceptable books - mostly adult history books.

I actually advocated to have her read lower books. I did not want her to dislike reading and to read what her friends were reading. At this point, I wasn't worried about her reading at a higher level.