When the government chooses to cooperate with private organizations to provide public services, the Supreme Court has made clear that the First Amendment prohibits religious discrimination. Three cases--"Trinity Lutheran Church of Columbia, Inc. v. Comer" (2017), "Espinoza v. Montana Department of Revenue" (2020), and "Carson v. Makin" (2022)--illuminate this concept. In "Trinity Lutheran," the Court held that Missouri unconstitutionally excluded a faith-based preschool from receiving state-funded playground resurfacing. In "Espinoza," it found that Montana's supreme court unconstitutionally invalidated a private-school-choice program because it included faith-based schools. And in "Carson," the Court held that Maine violated the Constitution when it excluded religious schools from a rural scholarship program. Read together, these three cases establish a clear nondiscrimination mandate: when the government establishes programs that extend public benefits to private organizations, it cannot exclude religious organizations from participating. This report details unconstitutional religious discrimination in public pre-K programs. The authors hope that this report will draw attention to pre-K programs that fail to comply with the Free Exercise Clause's nondiscrimination principle.