Either the people who watch Khan's video's find them useful, and can do things they couldn't do, or understand things better than they did, or not. Most public

Either the people who watch Khan's video's find them useful, and can do things they couldn't do, or understand things better than they did, or not. Most public school teachers are awful. They have degrees in education, and most university programs in the teacher pipeline are intentionally easier and less demanding than the equivalent 'real' degree in a given subject. 'Math-ed' is a very undemanding degree compared to 'Mathematics'. If high-school teachers were placed under this kind of scrutiny we would be forced to completely re-evaluate how teachers are credentialed and licensed. They aren't put under this or really any scrutiny at all, and probably they never will be. Teacher unions fight as hard as they possibly can to prevent any measurement or evaluation of teacher performance. Students will continue to try to fill in the gaps in their understanding of these topics, and if there are free resources available to them to do so, even better!