So liberty has nothing to do with it?
This is a government school we’re talking about. This kid’s family pays taxes which go to the school system. Equal protection cuts both ways. If it were a private school, this would be settled very quickly and decisively.
By the way, I don’t support the idea of public education at all. This is a perfect example of why.
I attended public school in the 50’s and 60’s. We had a dress code. I agree with dress codes. This has nothing to do with liberty. Schools where I live ask the kids not to wear band t-shirts. Should they sue? No.