a tiny bit a horribly bad advice inspired by a japanese comic:
get yourself a male uniform and wear it.
burn your skirts, just to be sure you can't wear them.
won't help your conflict with your parents, but... if you actually hate your uniform skirt, wouldn't it be really fun to try burning it?
if you don't want to burn it, donate it to someone who can't afford a new uniform.
you might also beg the principal to expel you, just so you can go to a public school?
maybe telling your parents first would be a good idea if you try getting expelled. just so they know why you're doing it, and that it's all their fault for not letting you be who you really are.
(these might be bad ideas though, i have no guarantee it will work, so it's best not to try)