Normal school uniform at that period also meant wearing quite tight black trousers, but it did also mean that girls wore micro skirts, often very tight ones. The type of skirt a girl wore in 1969 would simply be banned today. It certainly made slapping their bottoms very tempting, and after a few years of temptation I did start smacking a few, and it should be said not one girl objected, quite the opposite.
The only frustration was that no girls ever got the slipper in front of the class, though there may have been a few in private