This chapter examines the evolution of religious expression in American public education from the founding era through contemporary legal challenges. Beginning with the nineteenth-century common school movement, the analysis traces how public education emerged as a cornerstone of American democracy while navigating tensions between religious accommodation and constitutional church-state separation. The chapter chronicles the transformation from explicitly Protestant-influenced systems to increasingly secular institutions, highlighting key developments including the Catholic challenge of the 1840s–1850s, the Civil War’s impact on educational nationalism, and the Progressive Era’s scientific curriculum approach. Particular attention is given to landmark Supreme Court decisions shaping modern religious liberty jurisprudence, from First Amendment incorporation in Cantwell v. Connecticut (1940) through the 1960s prayer cases (Engel v. Vitale and Abington School District v. Schempp). The analysis demonstrates how contemporary conservative Supreme Court majorities have shifted toward protecting individual religious expression rights, often at the institutional separation’s expense. This trend is exemplified in recent cases involving public funding for religious schools (Trinity Lutheran, Espinoza, Carson), facility access rights, and the landmark Kennedy v. Bremerton decision that replaced the Lemon test with a historical practices approach. Key topics include school-sponsored prayer, religious displays and symbols, public funding for parochial education, release-time programs, biblical studies in curriculum, evolution versus creationism debates, and expanding religious expression rights for students and teachers. The chapter concludes by examining current controversies, including state mandates for Ten Commandments displays and Bible instruction, illustrating ongoing tensions between religious accommodation and secular education. This examination reveals how the evolving legal landscape significantly impacts school administrators, educators, and communities seeking to balance constitutional requirements with diverse religious perspectives in public education settings.