To what extent are adults and minors protected under the first amendment?

Although in the constitution it is meant to apply to everyone this is not the case in public schools. It is sometimes over looked for teenagers/students because they are less educated about their basic rights, and thus can be easily manipulated. For instance we have the freedom of speech but it is limited on campus. It is like abiding by another law when in school. Students' first amendment rights are limited because whatever actions they take effects the administration that is responsible for the teenagers.
(Tinker v. Des Moines is a famous 1969 case involving two students protesting the war in Vietnam by wearing black armbands to school. The principal, ostensibly apprehensive about the disruption such armbands may provoke, asked the students to remove the armbands. When they refused, they were suspended. In deciding the case, the Supreme Court ruled 7-2 that the armbands in this instance were sufficiently close to speech to be protected by the First Amendment, and that the principal failed to show that wearing them would substantially disrupt the school atmosphere. Justice Black and Justice Harlan dissented.)