It's very close to a patient telling the doctor what is wrong with him, then telling him what to prescribe.
Well, I disagree with you on both points.
A student worth his or her salt isn’t just listening to the Professor, or reading the associated text book either. That’s what “learning” is all about. They should be reading other sources other than the books that are recommended by the course as well. I suppose that most people are lazy and do not.
However, most people do go to courses with the idea they are going to learn something new to them, about the subject, in depth, and students certainly CAN tell you if a teacher is being lazy about teaching. (Having been an instructor myself for several years at the college level, and going to courses myself at various degree levels, I can tell you for a FACT when a Prof is being lazy).
VERY occasionally, I have run into something where a teacher was, as you said, dead on and I was wrong. I found that out myself by doing the extra legwork. That also means however, you can discover when a prof is NOT DEAD ON and wrong.
But, the evaluations are not on the material usually, but rather how the teacher interacted with the class, how the material was presented, and to what level the student “felt” he/she learned something.
Oh, and for the record, a Doctor DOES NOT ALWAYS KNOW BEST... it’s my body and I have full veto powers over anyone else, including doctors. Sorry - I don’t give someone “rule over my body” because they have a degree and neither should you. I wouldn’t probably tell a doctor he was an idiot, and then let him prescribe anything.