Is he responsible enough to remember that he has "different" math or reading or whatever?
I was subject accelerated when I was in school, and when the teacher said, "get out your reading," I just got up and left.
I think the move to middle school is a potential problem area. You probably will want to talk about the transitions with the middle school well before he gets there (6+ months ahead of time), but I wouldn't worry too much about it yet. Many, MANY things can happen between now and then, and there's no point in giving the school a reason to say no to the subject acceleration if they haven't already thought of it themselves!
But I'm far from an advocacy expert, so take this with a grain of salt!
