That's something I wondered about myself. Chris slept through classes when he wasn't reading goosebumps and handed in pretty terrible papers when he had an assignment. Why did the teachers let him coast through this easily? Why did they allow him to nod off and read shitty novels for children?
I only see two possibilities, either his teachers didn't give a fuck at all or Borb were involved. I could easily see Bob or Barb making angry phonecalls after their son got shit for sleeping in class or something. Then again, maybe the teachers were happy Chris' disregard of the current lesson at least meant there weren't any stupid remarks, questions or the likes and the class could proceed without interruption.
And on the other hand, his behaviour more than likely meant the other people in his class weren't that fond of him, I'd guess. It's one thing to get bad grades for half-assing it, but Chris got passing grades while pretty much doing nothing when others more then likely had to bust their ass to get decent grades. Sure, Chris is the "Special kid" in class, but in the long run it could lead to some people being iritated, I think.