This "problem" is a recurring complaint that I have heard my entire 60 years. Yes, there are many viewpoints expressed through fashion, and face it, those expressions often fly in the face of parents and other adult sensibilities. But clothing worn in schools is an old and minor problem. When I went through the school system we were not allowed to wear short pants ever. Now they do. It's no longer a big deal, and really, was it ever a big deal except to those who thought short pants showed off the student bodies and interfered with student concentration?
Look, clothing does not override good educational practices. This minor blip of a problem isn't new and it's probably not even a real problem to student education. It probably dogged the flapper generation too.