As some isolated communities do, the boys of the school developed their own vocabulary, which might have mystified any outsider listening in to our private conversations. Python-worshippers may remember the episode of the squadron leader's banter. But there was nothing intentionally secret about it, and the masters were probably able to follow it.
I've forgotten most of it by now, but a couple of examples come to mind. "Hard ched" meant "hard luck" (by way of "hard cheese" and "hard cheddar"). "The whack" meant being caned.
Because we all studied Latin, we sometimes threw in a few words of pidgin Latin for comic effect, or spoke English as if translating literally from Latin ("The match this afternoon is ought-to-be-watched.").
Once, at assembly, Mr Cromie got up in front of us all (evidently the headmaster had delegated this task to him) and announced that he had heard boys using the word "crappy". He presumed that those boys didn't know what the word meant, and suggested that we substitute the word "tatty" in future.
I don't think anyone took up the suggestion, but we found it amusing and somewhat to his credit that he thought of recommending a substitute instead of simply banning the offending word.
In the main changing room for use after sport there was a large communal shower area with multiple shower heads. On one occasion, a matron accompanying a visiting team was surveying the naked boys in the shower, and was overheard to comment, "They come in all shapes and sizes!" This was felt to be highly humorous and was much quoted thereafter.