The Behaviourists did lots of laboratory work on rats and pigeons. They had spectacular success at building up elaborate behaviours by using positive reinforcement to select fragments of the desired behaviour. The idea of training animals by beating them was killed off by experimental work.

I don't know the history of the decline of punishment in education. Perhaps there was real experimental work with children, perhaps not. I find it hard to care; given the animal work, the idea that beating works to encourage learning by children now lacks even minimal credibility.