In Tinker v. Des Moines, the Supreme Court ruled in favor of the students who wore armbands to school after finding that the students did not substantially disrupt the school environment.
The Supreme Court noted that students do not lose their First Amendment rights when they arrive at school but that students may not disrupt or impede their fellow students right to an education. The silent armband protest was not disruptive enough to get in the way of other student's education and was therefore permissible.