Why do educational institutions allows professors who are incompetent to continue teaching?

I just came from taking a biochemistry exam, at a reputable pharmacy school. Our professor may be a great researcher, but he is an incompetent teacher that speaks very broken English. All of his “lectures” consist of powerpoint slides with jumbled words, and he often cannot answer our questions – as he only knows what is on the slides. During this exam, there was a question with two, very clearly, correct answers.

After the exam, I approached him to ask him about it (after I had looked it up myself). He first argued with me, and then said that he was confused by my question. Then his research assistant/TA stepped in, and backed him up, using different (also incorrect) reasoning. I am 100% sure that I am correct.. This is not an isolated incidence.

How should I handle this situation? Who can I go to, and would they listen anyway? This is certainly not the first professor that we have had this problem with… and I know it will not be the last. It is our education, that we are paying almost $30,000 a year for… and it is society’s well-being that will soon be placed in our hands. I’d like to think that the school would be concerned about providing the best instructors and the best information possible. Why does the school not put a stop to this? Is it all about getting those NIH dollars? Is having a good research staff more important than producing well-educated, well-rounded professionals?