I agree with so many points here, but cazzz made a good point about the books being read in school possibly being of importance in various projects. Also, I assume that your son does comprehension. If he has to write his own account of a particular story, then by not having read it, he wouldn't be able to do the work. Whilst the stories may be "babyish" to your son, they also contain the correct, repeated punctuation and word sounds, which, by reading a more forward book, may get skipped. I think this's particularly the case with books like "The Hobbit". Your son may be able to read it well, but it's hard going, with it skipping from character to character, and points tend to get missed. Having said that, it's a great book for someone who's an avid reader, but perhaps should be read at home, where there's more time to digest it. Have a word with the teacher, and see if your son can move on ahead of the rest of his class, but if not, there'll be a good reason for it. Best of luck.