For some subjects it seems that the issue is not level, but quantity of work. They don't want to be seen as letting students get away with less work. Maybe the

For some subjects it seems that the issue is not level, but quantity of work. They don't want to be seen as letting students get away with less work. Maybe there's also something of a resentment about them not being needed when they encounter an autodidact? I had problems with an AP chemistry teacher who was angry that I was doing the homework in class instead of listening to the lecture. When I said that I thought textbook had explained the topic quite well, her reaction was extremely negative. The existence of the autodidact sort of threatens the proposition of school itself.