It is Catholic Schools Week, when the nation’s 6,429 Roman Catholic schools discuss their reason for existence, and try to attract attention—and students—as many struggle to survive against “free” public schools. But you don’t have to be Catholic—or Christian, or religious at all—to learn from Catholic schools. You only have to care about equality and freedom.

Catholic schools exist, quite simply, because public schools cannot treat all, diverse people equally. Catholics felt compelled to set up a system that taught their children beliefs and identities they believed were essential—and sometimes to escape outright abuse—even though it meant sacrificing their public schooling tax dollars to do it.

As envisioned by Horace Mann, the “Father of the Common School,” and other 19th Century public schooling champions, a primary mission of the nascent system was to shape proper, virtuous, American citizens. Probably the large majority of early Americans sincerely believed that meant being Protestant, and Catholics were considered almost the antithesis of this, both for theological and political reasons. Rather than voting as free-thinking people, many Protestants feared that Catholics would vote according to the bidding of their Vatican-controlled Church, threatening control of America by the Pope himself. And certainly, the Church had a track record of exerting power in Europe.

With the conviction that “American” was synonymous with “Protestant,” many public schools were de facto Protestant institutions. Students read from the King James Bible—unacceptable to Catholics, especially because it lacked official Church interpretations—said Protestant prayers, and learned lessons containing anti-Catholic invective. The Protestant flavor was not always enforced on Catholics, but other times it was brutally so. In 1859 Boston, for instance, a Catholic boy was whipped for refusing to recite the Protestant form of the Ten Commandments, and many sympathizing students were expelled.

As Catholic numbers grew, and requests for accommodations were repeatedly rejected, Catholics concluded that they had no choice but to establish their own schools, lest their children be repeatedly subjected to teaching they found immoral, and even official abuse for their beliefs. By their peak in 1965, Catholic schools educated almost 12 percent of all school-aged Americans.

Why is this an important lesson for everyone? Catholics established the largest set of parallel schools and are the most visible group to have been treated unequally for their beliefs by the public schools. But such inequality for countless groups is inescapable in a system in which the people are diverse, but single governments fund and run schools with taxpayer dollars.

Even after the U.S. Supreme Court essentially outlawed official religion in the public schools in the early 1960s, values-driven conflicts continued unabated. The terms just changed, increasingly pitting religious Americans against atheists and agnostics, the latter of which were, of course, treated unequally in religious public schools.

The 1980s and 90s were rife with “culture war” battles over everything from school prayer to history curricula, and such warfare continues today. The Cato Institute’s interactive database of values- and identity-based conflicts catalogues nearly 1,830 state and local throwdowns since 2005, a large percentage of which involve religious beliefs in conflict with the strongly held, but mutually exclusive, moral values of other people.

Consider a recent burning fight: bathroom access for transgender students. Many people sincerely believe that students must be able to choose facilities for the gender with which they identify. Others are equally convinced that people of different biological sexes should not share such private spaces. Fundamentally, government must not impose one group’s beliefs on any other, but public schools cannot avoid making some decisions.

What is the solution to this conundrum? Simply fund students, not schools. Instead of setting up pitched battles to control a single school system, attach money to children, give educators autonomy to teach what and how they see fit, and let diverse people freely choose what their kids will learn. Make school choice—nearly 470,000 students are in private school choice programs today—universal.

What is the Catholic Schools Week lesson for everyone? In a diverse society, public schools cannot treat all people equally. But whether you are an atheist, Muslim, Roman Catholic, or anyone else, equality under the law is essential. School choice is the key to getting that in education.

Neal McCluskey (@NealMcCluskey) is a contributor to the Washington Examiner's Beltway Confidential blog. He is the director of the Cato Institute's Center for Educational Freedom and maintains Cato's Public Schooling Battle Map.

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