I had a biology teacher that was ridiculously mean to the students. It is apparent now that the reason for this, was because she was miserable with her own life. She shouldn't have taken it out on 9th graders.

I flunked that class horribly because I didn't have any desire to impress or please her, and I knew that a bunch of flunks doesn't look good for a teacher. The next year I took the course over with a different teacher and scored a 95.