That’s a good point. Gorsuch’s surprising cross over to rule with the liberal justices in a recent supreme court ruling (Bostock vs Clayton County) allowed gender and sexual identifies to be protected by current federal employment law. The very logical conclusion that comes from, any discrimination on the basis of sexual or gender identity revolves around a person’ s assigned sex at birth, which is definitely prohibited, and you can’t discriminate on those things without it being an illegal discrimination test based on sex. Basically if you fire someone assigned male at birth for wearing a dress but not someone assigned female at birth for wearing a dress, this is sex discrimination, already protected by current federal law. Similarly if you’re firing a male for marrying a male but not firing a female for marrying a male, than that’s sex discrimination already prohibited by current law.
Unfortunately I don’t know if the current Supreme Court reasoning would extend the existing federal law to protect non binary honorifics, since the school could argue it would fire anyone using a non binary honorific regardless of that person’s assigned sex at birth. Though maybe if you could get the school to admit they’d allow a non binary honorific for an intersex individual that would open up the door for non binary protections too via current law? But this is why we need a real updated federal law explicity protecting against discrimination on the basis of sexual and gender identifies, including non binary identities. In the meantime the states that do have explicit protections in their state laws are going to be much better places for non cis and hetero people to work in.