I didn’t mean school uniforms, I meant normal clothes in schools that don’t have school uniforms.
As for authors, it doesn’t bother me if they choose to have their characters wear whatever they want at school or if they choose to apply school dress codes and uniforms since every school is different and so is every story. I can agree though, that it isn’t nice to shame someone for what they wear, however something very indecent must be brought to attention to deter it from happening again because it can be totally inappropriate or even offensive (in any setting, but specially an educational/school setting).
Also, you should check this article from Insider to see what I mean: Outfits That Violated Dress Codes in US Schools