I took a computer class in college (like 25 years ago now?) and corrected the teacher multiple times every class. And it was like 95% things that were in the book that was issued, so I could even point out the page it was on. It was absolutely embarrassing.
In college I one year had a physics teacher who refused to believe that you could hear the harmonics of a guitar string simply by lightly touching the string at the right place, e.g. in the middle (12th fret) to hear the octave. Nothing could convince him that this was possible. That year was when several of us spent a good part of the week bowling in a nearby bowling hall, either because we didn't have to take the class (the curriculum was years behind what we had already done before college), or the teachers were so incompetent that there was no point attending. Fortunately the other educational years (everything after middle school, that year excepted) were great though.