"I needed it in college" is the answer to "when have you needed calculus after high school." In fact I was wrong though: I had forgotten that calculus was a prerequisite for AP Physics in high school. We also did plenty of probability in high school. I will say that Bayes and information theory in college were really cool and would have been a cool hook for teaching something in high school though, but there's only so much time. Had I taken AP Statistics they may have come up..