I was supposed to. In my high school, it was very much the case that you'd go to class if you were enrolled. However, it was also very much not expected that someone would take the cross-section of courses I took, so scheduling didn't take that into account. The registrar was faced with the choice to either tell a star student to take "dumber" classes or to let me take courses on my own terms and check their scheduling more carefully in the future.