As a student: The instructor who told everyone else that the class was cancelled, except for me, who drove an hour to get there and the teacher who gave us a badly drawn Baltimore pattern and got cranky with me every time I asked her to give me some instruction. I had never done needle turn, did not know about applique pins etc and she wanted to sit in the corner with a cup of coffee whilst I got on with it.
As a teacher: The student who turned up half way through the lesson, got equal amount of time and all the notes given to her and insisted that she should only pay half the lesson fee when they were only being charged $10 per head in any case.