I was inspired to ask this question by a 9th grade class I taught on Friday. Usually it's a difficult group, with lots of interruptions, but we've started giving a grade which is based on contributions to class (both positive and negative), so I'm now keeping track of interruptions and also of positive contributions to class. The kids saw I was keeping track and behaved much better. That's great of course, but I'd like them to be motivated by something besides grades. I do try to talk about the "why" behind what we study and get them to look for answers that don't involve grades or preparation for the next school year or university. They seem to know that "why", but I wonder if it's just something they're aware of, instead of something they really buy into. What do you do to build intrinsic motivation?