What is the "Lemon test" used to determine whether a religious invocation or benediction in a public high school graduation ceremony violates the establishment clause?

[53 Cal.3d 940] The majority correctly reason that the "Lemon test" (Lemon v. Kurtzman (1971) 403 U.S. 602, 612-613, 91 S.Ct. 2105, 2111-2112, 29 L.Ed.2d 745), governs our consideration of plaintiffs' establishment clause claims. The issue in Lemon v. Kurtzman, supra, 403 U.S. 602, 91 S.Ct. 2105, was whether statutes which authorized limited state financial aid to church-related elementary and secondary schools were constitutional. The question addressed in this case, whether inclusion of a "religious" invocation or benediction in a public high school graduation ceremony violates the establishment clause, was not directly presented, and the high court has not yet addressed the question.