As far as I recall reactions to the slipper were mainly a function of age, sex and number of strokes. Junior School (8 to 11+) was where I first encountered the slipper. It was used exclusively by the relatively few male teachers, mainly on boys, but not uncommonly on girls. It was always a public punishment, administered in front of the rest of the class, usually with the recipient bent over a desk in the front row, facing the class. This was the early 1950s and desks were rigidly arranged in rows and columns.
One or two strokes were the norm, and sometimes produced tears, especially in the earlier years. More commonly with girls, probably because in those days girls were supposed to be better behaved than boys, and there was undoubtedly more loss of face for a girl in incurring a punishment.