Arizona grants income tax credits for contributions made to school tuition organizations (“STO”). These STOs must use these donations for scholarships that allow students to attend private schools. This statutory scheme broadens the educational opportunities for thousands of students by enabling them to attend schools they would otherwise lack the means to attend. The Ninth Circuit held that the tax credit program violated the Establishment Clause because many of the STOs—as it happens, a decreasing majority—provide scholarships for students to attend parochial schools. Counsel for the defendants, including the Institute for Justice, asked the Supreme Court to review the case—and indeed to summarily reverse the Ninth Circuit, based in part on a 2002 case (Zelman v. Simmons-Harris) rejecting a similar challenge to a school voucher program. Cato filed a brief, joined by the Foundation for Educational Choice and the American Federation for Children, supporting this request. Our brief argues that the funds received by STOs are the product of individual taxpayers’ “genuine and independent choice”—the touchstone by which the Court judges the religious neutrality of statutes allowing for taxpayer money to fund religious education. Moreover, the tax credit scheme is indistinguishable from similar charitable tax deduction programs that the Court has previously held to pass constitutional muster. While the Ninth Circuit reasoned that Arizona parents feel pressured to send their kids to parochial schools due to limited scholarships available for secular schools, it failed to consider that the share of STO money available to secular schools was nearly twice as large as the share of families choosing to send their children to secular schools. Far from being an impediment to parental freedom, the autonomy Arizona grants to taxpayers and STOs is ultimately essential to it. More generally, should the lower court’s opinion be allowed to stand, the progress made to broaden the educational opportunities of students across the country will be stifled.