[Excerpt] A recurring issue in constitutional law concerns the extent to which the Establishment Clause of the First Amendment imposes constraints on the provision of public aid to private sectarian schools. The U.S. Supreme Court's past jurisprudence construed the clause to impose severe restrictions on aid given directly to sectarian elementary and secondary schools but to be less restrictive when given to colleges or indirectly in the form of tax benefits or vouchers. The Court's later decisions loosened the constitutional limitations on both direct and indirect aid. This report gives a brief overview of the evolution of the Court's interpretation of the Establishment Clause in this area and analyzes the categories of aid that have been addressed by the Court. The report explains which categories have been held to be constitutionally permissible or impermissible, both at the elementary and secondary school level and at the postsecondary level. The report also briefly addresses a set of cases (Arizona Christian School Tuition Organization v. Winn; Garriott v. Winn) currently before the Court regarding the constitutionality of an Arizona statute that permits individuals to claim a tax credit for certain donations to school tuition organizations that use the funds for scholarships to private and, in some instances, religious schools.