Wear them anyway, and push the regulations to the limit. Only dweebs obey the rules, because the teachers are too busy preparing for the final year exams
Go for it. if you get asked to change, then listen, but most likely you won't. If you feel good in them and think they are flattering on your body type, wear them! if not, wear what you want to wear.
When I was in 7th grade, we weren't allowed to wear skinnies either. At first I wore slacks and looked like your typical school boy lol. But half way through the year I wore skinnies of the school color code and they didn't even care lol.
Skinny jeans are hideous looking and out of style. That's why they aren't allowed. Just wear flare jeans. They are stylish and flattering and look better dragging the floor. Why do you want your bottom half to be shaped like an icecream cone?