Coming hot on the heels of Everson, decided the previous year, this case was an early test of the separation of church and state as regards education. In addition, McCollum was the first test, and defeat, of the concept of "released time", wherein a school might set aside time during the class week for students to attend separate religious instruction.

The Illinois School Board had set up a program wherein students could receive religious instruction -- Jewish, Catholic or Protestant -- for a stipulated period during the school week, within the public school building, but taught by outside instructors not in the pay of the school district. The school maintained the right to approve the instructors, and students not enrolled in the program by their parents stayed in other parts of the school building.

The Court found the program to be clearly impermissible state support of and aid to religion, in violation of the First Amendment Establishment Clause. Writing for the Court as he had in Everson, Justice Hugo Black pointed out the historical basis for avoiding the commingling of secular and sectarian instruction in public schools, and noted that at that time there were over two million students involved in such "released time" programs nationwide.

In dissent, Justice Stanley F. Reed argued that the First Amendment should be read more narrowly so as to permit such incidental support of religion by the state.

In reaching its decision, the Court did not specifically address the location of the instruction in question, only the involvement of the public school system in its administration, organization and support. In Zorach v. Clauson, decided in 1952, the Court muddied the waters of McCollum just a bit as, in a desire to show support for religion in general, it held that a similar New York program which supported "released time" instruction outside of school property, did not violate the First Amendment. Dissent in that case -- by three of the majority in McCollum -- argued that location was not a crux issue in McCollum, and that since the school district in Zorach supported the program with attendance records and action against truants, it still aided religion beyond the constraints of the First Amendment.

Justice William O. Douglas, who later evolved into a strict separationist, wrote the Zorach opinion, using words often quoted in support of accommodation. Justice Douglas stated that "we are a religious people whose institutions presuppose a Supreme Being."

Such thoughts waned as the religious fifties evolved into the secular sixties of the later Warren Court.