That "nobody checked" comment brought up another memory, the gym teacher said there would be "Jock checks". I don't remember ever going through one, though.
We didn't swim naked, as the pool was somewhat open. Gym classes were segregated, but it would have been pretty easy for anyone to come into the pool area. We did wear school-issued suits, nylon and kind of flimsy; I remember one guy dove into the pool from the deck and from the obvious hang as he was momentarily horizontal, he was obviously well hung. He confirmed Xaviera Hollander's statement in "The Happy Hooker" that you could tell the size of a guy's cock by the size of his nose.