As a fifth grade teacher and a parent as well, I would suggest that you let your child lead you. First, make sure he is reading material he understands and enjoys. Don't just choose it because it is on the "fifth grade level". These topics may not be interesting or even relevent to his limited experiences. Consider asking the teacher help you choose a chapter book that is at the interest level of 5/6 year olds and allowing him to read it to the class. Most importantly keep in mind that a child that can decode and read words at a fifth grade level may not be ready for fifth grade content. Be sure you do not discourage him by pushing literature that is not interesting to him and his limited years of world experiences. It is okay for him to read picture books if that is what interest him... and he will continue to grow in his level of comprehension and experiences.