I taught high school math (3 years in conventional American public schools, 3 years in the Peace Corps in Ghana, and 5 years in a contract school on the Navajo reservation), then went to grad school and got re-treaded into a college professor. I now teach prospective teachers how to teach math (both elementary and secondary). I'm a better teacher of teachers than I was a math teacher--sometimes these days I think I'm beginning to understand what I'm doing at least a little bit.