Here are a list of precedents for the case.
 
-Tinker v. Des Moines (1969):The Supreme Court ruled that "students do not shed their constitutional right to freedom of speech or expression at the schoolhouse gate."

-Cohen v. California (1971):The Court upheld the right to express an anti-draft viewpoint in a public place even though it was delivered in terms highly offensive to most citizens.

-New Jersey v. T.L.O. (1985):The Court ruled that the constitutional rights of students in public school are not automatically coextensive with the rights of adults in other settings.

Texas v. Johnson (1989): The Court ruling said that the Texas law violated the First Amendment since it determined that the prosecution was directly related to expression.

Bethel v. Fraser (1986): The Court ruled that "the constitutional rights of students in public school are not automatically coextensivewith the rights of adults in other settings.”

Brandenburg v. Ohio (1969): The Court ruled "punishing someone for advocating illegal conduct is constitutional only when the advocacy is likely to pro-voke the harm that the government seeks to avoid."

Rosenberger v. Rector of Univ. of VA (1995): The Court ruled that "the government must abstainfrom regulating speech when the specific motivating ideology or the opinion or perspective of the speaker is the rationale for the restriction."

Hazelwood School Dist. v. Kuhlmeier (1988): The Court ruled, "the rights of students must be ‘applied in light of the special characteristics of the school environment."

Vernonia School Dist. v. Acton (1995): The Court ruled "the nature of ...(student) rights is what is appropriate for children in school.”

Thomas v. Collins (1945): The Court ruled in a case which "overturned the conviction of a union organizer who violated a restraining order forbidding him from exhorting workers...we held that the distinction between advocacy and incitement could notdepend on how one of those workers might have under-stood the organizer’s speech. That would “pu[t] thespeaker in these circumstances wholly at the mercy of the varied understanding of his hearers and consequently of whatever inference may be drawn as to his intent andmeaning.”