It is long past time for schools to enforce some type of dress code for their students. People can bleat and blather all they like, but high school students are NOT adults and should not be allowed to act like them.
I've told both my kids that they will not be allowed to "express" themselves through their appearance until they can first express the given idea in both written and spoken form eloquently. Appearance expression will be forbidden until other forms of expression are mastered. Most kids (amd parents) have it backwards.
Even after they submit their written and oral essays about "the injustice of the world" or their inner angst, anything that permanently alters the body that God gave them is expressedly forbidden.
For instance, purple hair will be OK, as long as they can coherently and persuasively express just what message the purple hair is supposed to convey.
Schools used to be about setting standards for students, including dress and appearance. There was general agreement about civilized behavior. We can blame the 60s and its enforcers, like the ACLU, for the idea that barbaric dress and behavior are seen as protected expressions of "individuality." I wonder how many of these self-important, in-your-face "individualists" has ever had an independent thought.
As for the "supportive" parents--no thanks for contributing to the decline of our civilization.