I don't like uniforms. I had a uniform when I was young. I did not care that much as I had pants, a shirt and a sport-jacket like jacket. Any coat over this on the way to school. Girls on the other hand had to wear dresses, which were much thinner and much more exposed, especially to the cold which is what I would care about most. Walking with a skirt or shorts in the cold is not fun and I would not curse it on anyone.
I also do feel that dresses and skirts are extremely sexist. Can you imagine how many puled up dresses there are. There were a lot at my grade school, can't imagine what it would be in a high school. Also, easy sexual or rapist access, which is also not good.
I enjoyed those nice cheerleader outfits, but as much as I would enjoy it I would not want to force this on all the girls in the school even with longer skirts.
Myself, I always wore a hoodie to school, and I wear one to work now, as I get cold easily, even from a little extra AC and the connected hood is much better then any hat.
So I think that any functional clothing may be worn, like in this case warm clothing without restrictions. Baseball hats, I think do little, but I have been in classes where a sweater or hoodie and a hat or earmuffs are an absolute must.
I have taken an exam in a very cold room, I wore a winter jacket and felt great, I just could not take it off, not an issue for me.
I have also taken exams when I forgot my jacket, on a hot day. I flew through the exam with my hands and body shaking profusely and ran out of there, needless to say I did not do to well, but I passed.
So the wrong dress code will kill my ability to perform in school, and probably at least hurt everyone else.
Oh, I think the suspension is ridiculous. I would like everyone in the school to breach the dress code and everyone to be suspended, so they can go to a different school or have the administration of their school changed.