Some professors are just laughable. The fuckin' idiot shows up 20 minutes late and the first sentence he says is "60% of you will fail this semester, it's up to you students to pass, don't blame the professor so if you fail it's your fault" No one even said a word and he started that shit!
I had entire physics classes as an undergrad where I abandoned the prof's lectures, got a bunch of students to join me, and we held "dark" lectures in parallel where we thought we could actually learn something ourselves together. We did better than we could from the prof's lectures, that's for sure. We just had to keep an eye on when he might schedule surprise quizzes.
