Being made to run up and down ice covered stone steps barefoot was an isolated low point, but being put into the first XV rugby squad as cannon fodder because the teacher hated my mum, who also taught there, set the general tone. https://twitter.com/emigarside/status/1285883708516569091
NB - these were different schools and different teachers. The attitude was the same.
I can add: being made to play rugby in a blizzard - stuck at full back (because i was “less damage to the team back there”), not running about because I couldn’t SEE anyone else. Ended up with pneumonia that nearly killed me.
And, more bizarre than serious, being forced to referee a basketball match despite never having played or knowing the rules.