On the other hand, I've heard that in some places, Muslim people have problems at school because of the dress code as well, so I just think schools have to be more open to people wearing whatever they want.

So strange to judge by clothes

I never thought there was any problem with it

Cstar is no longer here, but this is a good discussion.  This happened 7 years ago. The girl was wearing exercise clothes.  I think now rules have been relaxed a lot and it would no longer be a problem.

Appropriate for the gym or lounging around the house.   For school, while she is covered, what's wrong with jeans/slacks/dress/skirt?   Then again, I'm a big supporter of uniforms for ALL schools, both public & private.  I think the "dress however you want" has gone a little too far - which is why we see people in the pajamas & slippers all over the place.  

I don’t mind uniforms.  It takes away pressure for students to decide what to wear and it’s less expensive.

Japan uses uniforms for all of their public schools. Even many of the private schools have their own uniforms too, but they're a bit different than the public school uniforms. Only a few private schools don't use uniforms.

FWIW

I’ve seen Japanese school uniforms. They seem to be somewhat trendy.  At least they are wearable.  That could be why Japanese teens have such strong senses of fashion outside of class.

This is from Japanese education system polls... it looks like some schools are moving away from traditional uniforms today for more trendy uniforms, but not when my kids went through school.

Elderly, everybody wore the traditional high collar ones, but as the age goes down... so do the numbers in favor of the newer uniforms increase...

Japanese Schools and Uniforms - JAPAN Educational Travel (jnto.go.jp)

FWIW

Skirt length for girls makes the difference because rowdy and trendy.