Research from the 1940s until recently that I am aware of. I’m not sure what you mean by ‘those policies’ though.
The policies of not punishing girls.
Plenty of teachers did use it with girls.
I know some did – with very good results.
You claimed that commonsense had already told the teachers what you claim the research subsequently showed. The researchers do not make the claims you do ( in general they claim CP is harmful to both sexes) so I’d like to know why you think the policy of not caning girls was based on “commonsense”.
Because it is. The data is clear and simple. There are some researchers who ignore their data and say otherwise, but not many. The view I am expressing is pretty mainstream and has been for most of the last decade.