IMO, acceptable outcomes to this are:
- Enforce the no head coverings rule equally
- Repeal the rule
- Allow head coverings for modesty, but don’t allow distracting or purely decorative hats
Personally, I’d opt for 2, replacing the current rule with a few guidelines to prevent trouble. For example, allow form-fitting head coverings in white, brown or black that don’t cover the face. It would even be reasonable for the school to loan a student an appropriate version, so as to prevent a disruption of education.
As far as I’m concerned, saying that only religious hats are allowed is elevating religion. People with no religious beliefs end up with fewer liberties than others. This invites the creation of spurious new religions, forcing the government to start deciding (establishing) which are legitimate and which aren’t.
Of course, sometimes I wonder whether we should protect religion at all. Unlike gender and race/nationality, religion is a matter of personal choice. Instead of trying to specifically accomodate every variation, the government should enact the least restrictive rules possible that accomplish necessary goals, giving equal weight to the opinions of all citizens (not favoring the religious hat-wearer over the modest hat-wearer). For example, instead of prohibiting employers from firing people who take off on high holy days, prohibit them from firing people for taking up to five personal days, provided they are scheduled 3 months in advance.
There are reasonable secular solutions to almost all of these kinds of issues. Instead of favoring one religion above the rest, they end up making life better for everybody, and still allowing us to easily outlaw the bad stuff (animal sacrifice, marrying minors, gender discrimination, etc.). All without sliding down the slippery slope to establishment.