The school may not display religious symbols on school property in a way that would endorse or appear to endorse religion. [1]  It’s not always clear whether an exhibit clearly sends a religious message.  Certainly, a cross or Nativity scene would be impermissible, or posting the Ten Commandments in classrooms. [2]  At the holidays, Christmas trees and even the Jewish Menorah or Islamic Star and Crescent are by now considered secular symbols, not religious. [3] 

In general, with holiday displays as in every other question of religion in school, the guiding principle remains that government must maintain a course of neutrality among religions as well as between religion and non-religion.  Accordingly, schools should keep in mind that an attempt to present a display or program that includes many religions may raise questions since many students either do not have any religious beliefs, or follow faiths (such as Islam) that do not have any holidays around Christmas-time.

[1] Allegheny County v. Pittsburgh American Civil Liberties Union, 492 U.S. 573 (1989)(striking down a Christian Nativity display at Christmas on courthouse steps).

[2] Stone v. Graham, 449 U.S. 39 (1980)(striking down Kentucky statute requiring posting Ten Commandments in every classroom, financed by private donations).

[3] Skoros v. City of New York, 437 F.3d 1 (2d Cir. 2006).