Actually, the school I went to in the late 90s insisted on "non-branded, plain black skirts or trousers" regardless of gender. Jeans, tracksuit bottoms and shorts were not permitted. Come summer the boys were less than impressed that they were sweating in trousers while the girls wore short skirts. So a bunch of year 11 boys who had been sent home for wearing shorts came in wearing skirts, refused to go home, and told everyone who asked (so in other words, everyone) why they were doing it. The head accepted the protest, accepted that if girls could wear skirts there was no real reason to send the boys home for doing it, and agreed to have a meeting about uniform. The uniform requirement was amended to "non-branded, plain black skirts, trousers or shorts (in summer)." I feel that this incident was effective in teaching the pupils - and the staff - about reasoned debate, equality, compromise, and non-violent protest in a democratic society. However I cannot see it being replayed in a faith school when the non-faith girls are getting too hot in the unaccustomed drapery around their heads and ask why they can't wear what the boys do.