I see.

I wouldn't say the kid is telling the teacher in confidence - if the kid asks the teacher to call them a different gender, other kids will immediately tell if Sarah is suddenly called Brian for example.

Abusive parents are something we will always have to deal with, providing schools with the ability to actually help is the only way to handle it IMO. If schools aren't given the ability to meaningfully help, I do feel they should steer clear of this entire topic.

I agree that coming out is a big deal, but I feel gender changes should be handled with an extra layer of support which typically requires parental help because they are underage. I don't trust British teenagers to act responsible without parental involvement and I don't trust parents to help teenagers properly in this situation, which is why I think the school needs to be involved fully or not at all.