All joking aside, schools are not Constitution Free zones. They are government institutions and they just can’t limit free speech like this, for terms that are not disruptive or vulgar but that the administration simply don’t like for personal reasons.
Students & Youth Rights

The Florida Constitution calls for a “uniform, efficient, safe, secure, and high quality system of free public schools.” The ACLU of Florida believes that schools are not constitutional dead zones, and yet students are often subjected to unreasonable searches, restrictions on their First Amendment rights, discrimination, and harassment. And more than fifty years after Brown v.

ACLU of Florida