Implicit in the First Amendment is to guarantee the individual right to conscience. The Establishment Clause was intended to prevent citizens from being forced to support a religion or religious exercise that may be contrary to their own beliefs. We have recognized in a wide variety of constitutional contexts that the practices that were in place at the time any particular guarantee was enacted into the Constitution do not necessarily fix forever the meaning of that guarantee. Even if we were to assume that the Court's practice of invoking a deity and the legislature's practice of state sponsored prayer were constitutionally acceptable, there are several major differences between public schools and our courts and legislative bodies. Student attendance in public schools is compulsory.
Truancy is against the law.
Legislators voluntarily seek election. They are not required to attend sessions or appear in time to hear prayers at the start of the legislative day. There is also a major difference in the mindset of the two audiences. Some studies, utilized by the Court, have shown that adults are not susceptible to religious indoctrination, but children are subject to peer pressure. Additionally, the public schools are incubators for democracy.