A friend of mine managed to get nine strokes at aged 14 at a Surrey secondary school by dint of being caned by two separate teachers after school on the same day. He didn’t mention that he was due to see the other teacher and in fact got an extra stroke for being late for his second appointment. Thus he received four and five strokes.
It was at a school flagged on Corpun as being a high caner in the late 60s. I suspect that teacher (rather than headmaster) punishments were not well documented.
I encountered my friend on his way home and he didn’t seem any the worse for his “ordeal”.