Whats wrong with allowing anyone to wear pants if they want?
The problem is this ruling could also potentially deny people the right to wear skirts if they want.
Schools would not be allowed to have skirts as a uniform item. So girls who want to wear them can’t. That’s not automatic, but it’s a real possibility.
Secondly, it’s about discipline. I realise the US doesn’t have a big tradition surrounding school uniforms but British schools do and they are a useful tool in teaching kids that there are rules in life and that they have to be followed.