Personally, I don't have an issue with the teacher's assistant aspect. Whether it was the teacher using me or just classmates seeking me out on their own, I did that all through school, and I've found it comes with these benefits:

1) Nothing exposes my ignorance of a subject as well as attempting to explain it to someone else.

2) Nothing helps me make wider connections with disparate information as hearing someone else's interpretation of a particular bit.

3) From this experience, the career-enhancing ability to take complicated technical issues and transform them into language that's commonly accessible has come fairly naturally.

I have zero tolerance for using the well-behaved child to influence the poorly-behaved child's behavior, though.