It seems to be generally accepted that no one teacher can manage a class of boys and girls if they have separate changing accommodations because while the teacher is supervising the girls the boys will murder each other and vice versa. As a consequence, they frequently change together in the classroom.
No, it isn’t murder, its bullying. Surely you came across that? In my day rife whenever the teacher’s back was changed, and especially in the changing rooms, where the budding members of the Gestapo or Stazi took their cue from their great heroes – the bullies in chief – PE Staff.
And I saw that slipper come out for a lot of things, other implements too- but never for bullying, which led the staff to a good old belly laugh in the gym.