We also had a willy watcher / closet paedophile in the PE department, like some of the tales from earlier, after rugby he would make the cleaner lads roll in the mud as they "hadn't tried hard enough". Then it was into the communal shower where he'd watch each and every one of you "to make sure you were properly clean", no in-and-out, extra-quick washes allowed, he wanted to drag the experience out clearly. He encouraged horseplay amongst the lads, and he liked passing comment on which lads were hairier and which hadn't developed as much, dressed up as fairly gentle ribbing but clearly, in hindsight, pretty sinister. He would also make you swim nude if you had forgotten your swimwear.
The other games master Gaz did monitor the showers but far more respectfully, I.e. he allowed the lads some privacy while they were undressed. I often wonder if he recognised at the time that he was working with a paedophile. I'm not sure we did, we certainly thought he was odd, and cruel, but the more sinister side only becomes apparent in hindsight.
These days that would be a police investigation thankfully. It's amazing and quite sad reading this thread, to see just how common that abuse of trust / power was.