Students and teachers do not “shed their constitutional rights to freedom of speech or expression at the schoolhouse gate.” The Supreme Court has made clear that “private religious speech, far from private religious speech, far from being a First Amendment orphan, is as fully protected under the Free Speech Clause as secular private expression.” Similarly, religious expression and observances are also protected.

Guidance on Constitutionally Protected Prayer and Religious Expression in Public Elementary and Secondary Schools | U.S. Department of Eduation

Classroom Instruction & ReligionReligious AccommodationsReligious Exemptions
Religious HolidaysUnderstanding Area Religions