Everything about it. Everything everyone else has already mentioned.
I'll also add:
Hockey and netball in the snow ❄️ ❄️ wearing just shorts and t-shirts. Same for cross country too. No tracksuits allowed. Teachers would be standing there wearing their own tracksuits and a large coat each.
Communal showers where you were made to strip naked in front of all of your year group were horrific, as was being given just a couple of minutes to complete shower and getting changed before the next lesson bell. You were chucked out of the changing room in just your underwear if you hadn't managed it in time.
Being forced to do team sports was awful. Apparently though, there is/was no other type of sport or exercise! 🤔😠
The period register was really creepy and would probably be termed abuse now. They would literally look into your pants if you claimed to be having a period to check whether you were wearing a sanitary towel and bleeding onto it. Horrendous.
PE at school was for me a ritual of humiliation and school sanctioned bullying. It was all kinds of shit and not remotely enjoyable.
I was so glad that I managed to drop PE when I did my options for O Level (showing my pre-GCSE age there). I would have bunked off if I had had to continue it.
We were actually supposed to continue doing some form of PE each week even if not for exams. It never appeared on my timetable though and I wasn't going to say anything or complain about that. 😃🤣 They did suddenly notice the error two years later just as we were about to go on study leave but it was far too late by then. I never did PE again and didn't miss it at all.