The First Amendment, through the Fourteenth Amendment, prohibits states from enacting laws “respecting the establishment of religion.”  The state of New York required that each day students in public schools say the pledge of allegiance and say a prayer.  The law permitted students who objected to saying the prayer to absent themselves during the prayer.  A parent sued on behalf of his student that requiring the prayer was a violation of the Establishment Clause.

On June 25, 1962, the Supreme Court ruled in Engel v. Vitale, 370 U.S. 421 (1962), that states may not require students to say a prayer.  The voluntariness of the prayer and the non-denominational character of the prayer did not make the law constitutional.

Read more about prayer in school or the Establishment Clause:

Religious Freedom in America:  Constitutional Roots and Contemporary Challenges 

First Amendment Stories