IMHO, reading should not be about pushing yourself to read the most challenging material you are capable of, but about enjoying what you read. If it's clear that he is not going to have problems learning to read, I wouldn't worry about what he's reading or what level the teacher thinks he is at, personally. He may decide that he'd enjoy reading harder books, and if he does I'm sure the teacher will provide harder books for him to read. Until then, perhaps it'd be better for him to be challenged in other ways.
