In the 2001 case of Zelman v. Simmons-Harris, the U.S. Supreme Court ruled in a 5-4 decision that Ohio's school voucher program did not violate the Establishment Clause of the First Amendment, which prohibits government endorsement or support of religion. The Cleveland-based program provided tuition aid to parents who chose to send their children to private schools, including religious ones. Opponents argued this was indirect financial support for religious institutions by state government and thus unconstitutional. However, majority opinion held that since assistance was given directly to parents who could choose where they used it (including non-religious options), there was no violation; any benefit received by religious schools came from individual choice rather than state action.

In the dissenting opinion for Zelman v. Simmons-Harris, Justice Souter, joined by Justices Stevens, Ginsburg and Breyer argued that the Ohio program violated the Establishment Clause of First Amendment because it resulted in government-sponsored religious indoctrination. The justices believed that most of the vouchers were used at religious schools which could lead to a situation where state funds supported religious institutions. They also expressed concern about potential coercion as low-income families might feel pressured to choose religious schools due to lack of affordable alternatives. Furthermore, they disagreed with majority's view on neutrality arguing that just because aid was given directly to parents did not mean it wasn't aiding religion indirectly since vast majority ended up in parochial schools anyway. Lastly, they warned this decision would undermine public education by diverting much-needed resources away from them towards private institutions.