As luck would have it I suspect most of the parents don't work for the school district, so that policy wouldn't apply to them. I also suspect the school district really don't want the First Amendment lawsuits from parents who decide to exercise their freedom of expression to dress like Santa or wear whatever other items they choose too even if conflicts with the multicultural table guidelines.

Become ungovernable. They work for you. You outnumber them. Remind them of that.