Here are a list of precedents for the case.
Wolley v. Maynard (1977): The freedom of speech protected by the First Amendment "includes both the right to speak freely and the right to refrain from speaking at all."
West Virginia State Board of Education v. Barnette: The Court ruled that; "If there is any fixed star in our constitutional constellation, it is that no official, high or petty, can prescribe what shall be orthodox in politics, nationalism, religion, or other matters of opinion or force citizens to confess by word or act their faith therein."
Edwards v. Aguillard (1987): The Supreme Court has noted that "states and local school boards are generally afforded considerable discretion in operating public schools.
Epperson v. Arkansas (1968): "By and large, public education in our Nation is committed to the control of state and local authorities. Courts do not and cannot intervene in the resolution of conflicts which arise in the daily operation of school systems and which do not directly and sharply implicate constitutional values."
Tinker v. Des Moines (1969): The Supreme Court ruled that even
"teaching values " must conform to constitutional standards. The constitutional line is crossed when,
instead of merely teaching, the educators demand that students express agreement with the educators' values.