I have found that the best math teachers were from community college. One teacher explained the solution to a calculus problem I had developed out of curiosity , and it wasn't even on the curriculum. He didn't have to do that, but I appreciated he did
Some of the professors there were a little zany, and had questionable teaching credentials ("Oh! You're a local businessman? Come teach a course on business!"), but the enthusiasm and... interestingness... of the education hasn't really been paralleled in high school, 4-year college, or grad school, in my experience.