If you're at a UK public school, I'm fairly sure that's actually illegal? The government say that a schools uniform cannot discriminate on the basis of gender (and sexual orientation, I'm not sure if that's relevant here). Taken from the
Department of Educations school uniform policy, 'A school should also bear in mind the concept of “indirect” discrimination.This involves the
application of a requirement, which, although applied equally toeveryone, puts certain people at a particular disadvantage because of their gender, race,sexual orientation, religion or belief or
gender reassignment.' It also says 'Governors should be willing to consider reasonable requests for flexibility in the uniformpolicy for an individual pupil to accommodate particular social and cultural circumstances.'
I'm not sure if you've seen or looked into this at all, but it's pretty clear that what they're doing isn't allowed. Have you tried taking this to the Board of Governors at the school? If not a local MP? Good luck