If you can't get your point across during the 4+ hours you have in class you are failing as a teacher. If you have to repeat a process 300+ times to get it you are not teaching, you are making people memorize shit in the short term and that will kick them in the nuts in the long term.
The stuff I was expected to do the most I retained the least, because instead of learning the general use and application of each function I instead put all my energy on just getting the grunt work over with so I could move on to the stuff that was actually fun. Excessive testing can also completely fuck over student's test scores if they have even one minor weakness. My physics (favorite subject) teacher failed to properly teach Significant Figures, as a result I ended up losing half a point on every question for that reason alone. They just expected me to 'get it' through repetition (spoiler: I didn't) and ended up with a nearly failing grade, even though it was my best subject.
Ultimately I ended up specializing in game design (big mistake, have you SEEN the game's industry? It's basically a fraternity!) because it was the only course that didn't have any busywork. You learned the concept, applied the concept, and then proved you understood the concept, then you moved on to the next concept. At the end you prove that you are able to work everything together and then the course is over and you have everything you need to make a game. It was a really hard course and I almost felt like quitting at times but I don't think I've forgotten even a single it taught me, a point that was proven even further when I took a different game design course and aced it with zero effort.
Couldn't tell you how to do matrix math though. I just remember it being really really useful if only I remembered the rules all those years later.