I tend to be a fast learner/worker also and I'm pretty much always ahead of the rest of the class. I have had experiences with teachers who will point that out - some more nicely than others. Their degree of "nice" determines whether they will see my face again (LOL). I think some teachers are rather insecure, which makes them react in such a way. Like you, I would have felt very uncomfortable with the situation, but probably would not have the guts to walk out (although I would have liked to). Especially in this instance, when it was a group but not a paid class.