The worst teacher I ever had actually did me a big favor.
I was always a bookworm and in high school I was put in the honor's English program. My sophomore year, however, I got a teacher who genuinely had it in for me. I could give numerous examples of how badly she treated me, but one will suffice. We had a multiple choice test one day, and when I got it back, I discovered that several of my correct answers had been marked wrong. I compared notes with a classmate who had received 100%. Sure enough, we had the same answers.
Being naive enough to think it was an honest mistake, we approached the teacher to get my grade corrected. However, the teacher refused to change the grade. When asked why the same answers were marked as right on my classmate's test and wrong on mine, she replied, "I changed my mind about which answers were correct."
It quickly became obvious that no matter what I did, I would not get good grades in her class, an issue which was compounded by the fact that she taught most of the honors classes. I was left with two equally lousy option.
1) Stay in the honors program and resign myself to getting bad grades.
2) Return to the easier classes and be bored stiff (plus it wouldn't look very good on a college application that I had quit the honors track halfway through).
My mother knew about the issue, but she didn't realize just how serious it was until she got a phone call from the mother of one of my classmates. This particular classmate and I had never liked each other. The girl I considered my enemy went home in tears because I was being treated so badly.
Her mother had an interesting idea. Why not have me take the placement test at the community college down the road? I could take English classes there and, through the magic of dual credit, they would count toward my high school English requirements.
That's the story of how I became the only student in English 101 who was too young to drive. By the time I graduated high school, I had already completed 5 college-level English classes with a 4.0 GPA (and since I was enrolled, I went ahead and took some other classes too).
Not only did I get the satisfaction of going over the horrible teacher's head and excelling, the English faculty at the college was awesome. After high school I went to a college out of state, so if I hadn't had that terrible teacher, I never would have gotten to study under the terrific ones.