They're teenagers. Young cockerels will be chasey and opportunistic. Older roosters usually have more physical clout and don't have to chase and will attract the ladies with treats, so they usually don't need "training" (but were surely cheeky cockerels once as well!)
I don't allow my cockerels or roosters to hurt the ladies, but they usually don't. If they do, it's not a male I would keep.
ETA: The boys will mature faster than the girls also, so once the girls reach sexual maturity, they will start squatting for the male and he won't have to chase so much as well.
Belated welcome to BYC!
