On June 25, 1970, the Supreme Court issued its seminal ruling on prayer in public schools in Engle v. Vitale, 370 U.S. 421. In Engle, Justice Black wrote that a state sponsored prayer was in contravention to the Establishment Clause in the First Amendment, which was applicable to the states through the Fourteenth Amendment.
On June 17, 1963, the Court again ruled against state sponsored recitations in public schools from the Bible and of the Lord’s Prayer in Abington Township v. Schempp, 374 U.S. 203. The opinion, by Justice Clark, held that government must remain neutral between the establishment of religion and the free exercise of it.
To read more about the issue of state sponsored prayer in public schools, see The Battle Over School Prayer: How Engle v. Vitale Changed America, by Bruce Dierenfield, or Ellery’s Protest: How One Young Man Defied Tradition and Sparked the Battle Over School Prayer, by Stephen D. Solomon.