The PE master at the school I attended was quite free in the use of a plimsoll - not sure what size it was! It was always over shorts. The cane was reserved to the Headmaster; I never got it! One "sin" was smoking, if caught you were cane by him in his study, a room that reeked of the pipe smoke he used, and ironically he said "Smoking is a filthy habit!" as he whacked your arse
At my school for indoor PE we had to wear just white shorts nothing else and we had to be bare under our shorts. Any boy caught wearing underpants under his shorts had to remove his shorts and do the lesson in his underpants and was then slippered hard with a size 11 plimsoll in the changing room after the lesson. I attended a private school and, as you may know, at private schools the cane was often given across the bare buttocks. It hurt like hell but boys were sometimes proud that we got it bare in a macho sort of way.
At my school we had gym detentions. Workout, then cane - every boy had to strip down to only shorts, nothing else. Always 6 hard strokes - it hurt like hell and left vivid welts.
I love the humiliation of being watched. My regular guy used to let his wife watch me get a spanking or caning. The embarrassment, made me lose my erection to start with, then after a few strokes I was up again and hope she liked watching my stiff cock and red arse