Engel was not by any means the first constitutional test of the Establishment Clause of the First Amendment -- the clause requiring the government to refrain from actively supporting a given religion, church or religious viewpoint. In the previous fifteen years alone, Everson (1947), McCollum (1948) and Zorach (1952) had all successfully asked the Court to reaffirm that there was, in fact, a "wall" separating state and church.

In Engel, the Court was asked to define just how high that "wall" was.

The case involved ten public school students who objected to the use of a generalized prayer written by their school district, which went "Almighty God, we acknowledge our dependence upon Thee, and we beg Thy blessings upon us, our parents, our teachers and our country …"

In their quest to have this requirement declared unconstitutional, the students had the active support of the ACLU, which had been banging the anti-establishment drum since Everson, and of a variety of other interested parties -- notably Jewish organizations -- many of whom submitted amicus curiae briefs in support of the plaintiffs. (The presence of so many "interested parties" had recently become a mark of modern constitutional litigation, the harbinger of today's "professional activists".)

The position of the separatists, who viewed any state support of religion -- direct or indirect -- as unconstitutional, was not without historical precedence. Their case drew heavily on selected writings of Thomas Jefferson and James Madison, as well as the legal precedents mentioned above.

Although fewer in number, supporters of prayer were also well organized, and amicus briefs were submitted by twenty state attorneys general, and others. By and large the supporters felt that the spirit of the Establishment Clause was not violated in this case, and that the Free Exercise Clause supported the presence of non-coercive religious activities even in public schools.

The majority of the Court sided with the separatists and, while citing no precedent in his majority opinion, Justice Hugo Black raised the wall from mandating or coercing to mere "encouragement", stating that the use of public schools to encourage prayer was "a practice wholly inconsistent with the Establishment Clause". He added that, while religion need not be completely purged from public life, public schools may not sponsor it.

In his dissent, Justice Potter Stewart argued that the Free Exercise Clause was the preeminent of the two religious clauses in the First Amendment, and that the Establishment Clause was only meant to prevent government from establishing an official church. Though his arguments in this case, as well as Abingdon School District v. Schempp the following year, were unpersuasive to the Court, his thoughts were incorporated into the opinions of later members.