Rewrite this thesis statement to make it precise.

Some teachers can cause more harm than good.

The effect of poor teaching can have a damaging effect on a student's understanding of and appreciation for a particular field of study. In my case, at university I was turned off trigonometry by a nervous prof who would back up and knock the chair off the teacher's platform and go through the lesson much too fast to be able to grasp the concepts so I failed his course. Theand n when I bought an excellent book which explained trigonometry in a very sympathetic manner I was able to understand it and wrote a supp on it and got a B with my own effort.