Can Charter Schools Be Religious? The St. Isidore Case

No. A charter school cannot be religious. Federal law defines a charter school as one that “is nonsectarian in its programs, admissions policies, employment practices, and all other operations, and is not affiliated with a sectarian school or religious institution.”¹ That requirement is built into the federal definition of what a charter school is. Individual students and staff keep their own religious rights on campus, but the school as an institution cannot teach, sponsor, or organize religion.

The Federal Rule That Makes Charter Schools Nonsectarian

The nonsectarian requirement comes from the Elementary and Secondary Education Act, which sets out what qualifies as a charter school for federal funding purposes. Under 20 U.S.C. § 7221i, a charter school must be nonsectarian across the board, not just in curriculum but in hiring, admissions, and every other part of how it runs.¹ The statute also forbids affiliation with any religious school or institution. The federal Department of Education puts it plainly: “charter schools cannot charge tuition or be affiliated with a religious institution.”²

Most states repeat the same prohibition in their own charter school statutes. Oklahoma, for example, requires a charter school to “be nonsectarian in its programs, admission policies, employment practices, and all other operations” and separately bans charter schools affiliated with “a nonpublic sectarian school or religious institution.”³ So the ban sits on two layers of law at once, federal and state, and it functions as a legal condition of a charter school’s existence.

Why the Constitution Reaches Charter Schools

The statute rests on a constitutional foundation. The First Amendment’s Establishment Clause prevents the government from sponsoring, favoring, or commanding any religion.⁴ The Free Exercise Clause protects individuals’ right to practice their faith without government interference.⁵

Charter schools are public schools. They receive public money, they are tuition-free, and they must be open to all students.² That makes them government actors, and the Establishment Clause applies to them the same way it applies to any other public school. The Supreme Court settled the core principle decades ago in Engel v. Vitale, holding that state officials cannot compose or require prayer in public schools, even when the prayer is nondenominational and students are free to opt out.⁶ Charter schools get more flexibility than traditional public schools on curriculum and management, but that flexibility stops at the First Amendment.

What a Charter School Cannot Do

Because a charter school is a public school, the restrictions on institutional religious activity are broad.

No religious instruction. The school cannot teach religion as truth, build a curriculum around religious doctrine, or use religious texts as devotional material.
No school-sponsored prayer. The school cannot organize, lead, or require prayer or other religious observance, even if participation is technically voluntary.⁶
No religious displays that signal the school endorses a faith, such as crosses, scripture passages, or religious banners in classrooms and common areas.
No religious hiring or admissions criteria. The school cannot favor or reject applicants based on their religion.¹
No proselytizing by staff or by outside speakers the school invites.

The rule targets what the school does as an institution. What individuals inside the building do on their own time is a separate question.

What Is Still Allowed

Individual religious expression by students and staff does not disappear at the schoolhouse door. Students can pray on their own during lunch, free periods, or before and after school. They can wear religious clothing or symbols, and they can talk about their faith with classmates. The Free Exercise Clause protects that expression.⁵ The limit is that it cannot disrupt instruction or pressure other students.

Student religious clubs are also protected. The Equal Access Act gives students at public secondary schools the right to form religious clubs on the same terms as any other noncurricular group. If the school lets any student club unrelated to the curriculum meet on campus outside class time, it cannot turn away a Bible study, an interfaith group, or a similar club because of its religious content. Meetings must be voluntary and student-initiated, and school employees can attend only in a nonparticipatory role.⁷

Academic study of religion is fine too. A world history class covering the spread of Islam, an English class analyzing biblical allusions, or an elective on comparative religion all stay within the Constitution. The line is between educating students about religious traditions and training them in one.

Teachers keep personal religious freedom but exercise it within the limits of a public employee’s role. They can pray silently, wear a religious head covering, or keep personal religious items at their desk. They cannot lead students in prayer, work devotional material into lessons, or use their position to promote a faith.

The St. Isidore Case and Where the Law Stands

The biggest recent test of whether a charter school can be religious reached the Supreme Court in 2025. Oklahoma’s statewide charter school board approved a contract for St. Isidore of Seville Catholic Virtual School, which proposed an openly and pervasively Catholic curriculum. The Oklahoma Attorney General sued, and the Oklahoma Supreme Court struck the charter down, holding that it violated both state charter school law and the Establishment Clause.³

St. Isidore appealed. On May 22, 2025, the U.S. Supreme Court split 4-4, with Justice Barrett recused, producing a per curiam affirmance of the Oklahoma decision.⁸ A tie means the lower court ruling stands but does not create binding national precedent. The practical result is that states cannot be forced to charter religious schools, and no state currently operates one. The larger constitutional question is formally unresolved, but the combination of federal law and Establishment Clause doctrine makes it unlikely any state will successfully approve a religious charter school soon.

How This Differs from Vouchers and Private Religious Schools

Confusion often comes from the fact that public money can reach religious schools through voucher programs, even though charter schools themselves cannot be religious. The difference is who chooses and who runs the school.

In a voucher program, the government gives funding to families, and the families choose where to spend it, including at religious private schools. The Supreme Court upheld this in Zelman v. Simmons-Harris, reasoning that when public money reaches a religious school only because of a parent’s independent decision, the program does not offend the Establishment Clause.⁹ The money follows the family.

A charter school works differently. It receives public funding directly, operates under a government-issued charter, and must accept all students. There is no intermediary private choice, so the school itself is the government actor and the Establishment Clause applies in full.

Private religious schools sit outside this framework entirely. They are funded through tuition and donations, so they can build their whole program around a religious mission, require worship attendance, and hire and admit based on faith. Title VII specifically exempts religious organizations, including religious schools, when they consider religion in employment decisions.¹⁰ None of that is available to a charter school.

What Happens if a Charter School Crosses the Line

A charter school that engages in religious activity risks losing its charter. The charter is a contract with a public authorizing body, and violating the nonsectarian requirement breaches that contract. Authorizers can revoke charters for cause, and religious promotion qualifies. In the St. Isidore case, the charter was nullified before the school even opened.³

Charter revocation is not the only exposure. A school that engages in religious practices can also be sued by parents, employees, or advocacy organizations. Those suits can seek injunctive relief to stop the activity, and they can force the school to pay the plaintiffs’ attorney fees. For a charter school running on thin margins, the legal costs alone can be existential before the underlying claim is even decided.

1
Office of the Law Revision Counsel. 20 USC 7221i Definitions
2
National Charter School Resource Center. What Is a Charter School
3
Congress.gov. Religious Charter Schools Remain Unlawful in Oklahoma
4
Constitution Annotated. Overview of the Religion Clauses
5
Constitution Annotated. Amdt1.4.1 Overview of Free Exercise Clause
6
Justia Law. Engel v Vitale, 370 US 421 (1962)
7
Office of the Law Revision Counsel. 20 USC 4071
8
SCOTUSblog. St Isidore of Seville Catholic Virtual School v Drummond
9
Justia Law. Zelman v Simmons-Harris, 536 US 639 (2002)
10
Office of the Law Revision Counsel. 42 US Code 2000e-1 – Exemption