I see that a lot of posts here get criticised as "fantasy". Some no doubt are, but some seem rather plausible to me, at least consistent with my own experience of the tawse on hand from female teachers in front of mixed classes at Scottish primary school and later slipper and cane from male masters and prefects at boarding schools.

To answer the question, yes around 1960 when we were about 11 I actually watched someone getting slippered on the seat of his pyjamas by an attractive Scottish assistant matron (true I promise you) whose own room was next door to our dormitory. He was a bit of a cheeky troublemaker and I will never forget the look of righteous satisfaction on her face as she applied the slipper vigorously. He was bent over the edge of his bed which was close to my own bed, in fact she used my own bedroom slipper for the first couple of strokes then hurled it contemptuously to the floor when she realised its spongy sole was not getting through to him. She then used someone else's leather-soled slipper which would have been more effective, although less so than the headmaster's gymshoe which we were used to. Knowing this, I doubt if any of us in the dormitory were distressed to watch this beating which was received stoically, although there was no more noise in the dormitory that night.

Slipperings were more usually received in private, touching toes, in the headmaster's office or master's study but the assistant matron would not have wanted to take the boy into her own sacrosanct room when she was getting ready for bed so maybe that was why she gave this beating in the dormitory. She certainly made her point.

This public spanking and the fact that it was given by a female was very unusual at this school but not unique.

Hope this helps to answer the question.