Like 3pt141597, I remember everything about high school trig. Not only do I remember it, but as it turned out, 10 years after leaving school, I actually started having to use it regularly (graphics programming). I also remember high school level calculus. Sadly I can't say the same for university-level maths, which I regularly have to break out the text books for when I need them (stats and probability, complex numbers being my two regular bugbears).

When I think about it, I struggle to find a single useless class from high school. If anything, I regret mostly that I didn't make enough of the opportunities that my school provided me - I really regret not having put in the effort in art classes for example.