I’ve never seen a speck of evidence to suggest girls were ever strapped or caned on the rear by male teachers, except in circumstances where the man was subsequently charged with a criminal offence.
Stories about girls being slippered on the rear by males are usually fantasy but may well be true in some cases.
The main factor is the lifting of the skirt – canes and straps are slowed down tremendously by contact with a loose skirt and so are virtually useless unless the skirt is raised.
Slippers, in stark contrast, can make a significant impression even through a skirt.
Any male teacher who ever whacked any girl on the rear (skirted or otherwise) should have been sent to prison for a very long time.