America is engaged in “the world’s most radical experiment in democracy,” Heather McGhee of Demos notes, because we are “a nation of ancestral strangers that has to find connection even as we grow more diverse every day.” Our histories start in countries all over the globe, with different languages and different faiths, and yet somehow we have continued to work on forging a common democracy. If conservatives have their way, a new Supreme Court case to enable public funding of private religious education could make that work of forging social cohesion all the more difficult.

More than any other institution, our country’s system of public education has provided the glue that holds our nation together. Nine in ten American children attend public schools, which take all comers, no matter their race, religion, or income. To be sure, public schools need to become better integrated by race and economic status—a goal that The Century Foundation has championed for almost a quarter century—but American public schools are still the predominant driver of our national experiment, taking people from all walks of life and teaching them what they have in common as Americans.

The unique challenges of educating students whose family backgrounds start in all corners of the globe was not lost on early supporters of public education, which is why, so far, thirty-seven states enacted constitutional provisions to prohibit the use of public funds for private religious education. Making public funds available for each religious sect to form its own exclusive school would make the challenge of creating a common American identity all the more difficult.

Today, 75 percent of American private school students attend religiously affiliated schools. These schools serve as an important vehicle for families who wish to inculcate a particular religious set of beliefs in their children, and on their own dime. These schools are not, however, charged with promoting democratic values, or a common American identity, as public schools are, so there is good reason to reserve public funds for public schools.

Religious schools are not charged with promoting democratic values, or a common American identity, as public schools are, so there is good reason to reserve public funds for public schools.

Moreover, in some cases, religious schools promote undemocratic and pernicious practices. Take, for example, the Fayetteville Christian School in North Carolina. As my former Century Foundation colleague Kimberly Quick found, the school declared on its website that it “will not admit families that belong to or express faith in non-Christian religions such as, but not limited to: Mormons (LDS Church), Jehovah’s Witnesses, Muslims (Islam), non-Messianic Jews, Hindus, Buddhists, etc.” The school also says it “will not admit families that engage in illegal drug use, sexual promiscuity, homosexuality (LGBT) or other behaviors that Scripture defines as deviate and perverted.”

Under the Constitution, parents have the right to pay for private religious schooling. In a 1925 decision, Pierce v. Society of Sisters, the U.S. Supreme Court held that parents cannot be forced to send their children to public school and instead have the right to spend their own money to educate children in religious school. But there has been no constitutional right to have the public foot the bill for private education. Indeed, there are powerful policy reasons for the public not to do so. As Michael Kelly, the late editor of The New Republic noted, “Public money is shared money, and it is to be used for the furtherance of shared values, in the interest of e pluribus unum.” Schools that divide us by such factors as race or religion “take from the pluribus to destroy the unum.”

Soon, however, that delicate balancing of values—in which parents have a constitutional right to use private money for private schools but policymakers prudently choose to reserve public money for public schools—may be undone. In what conservative commentators are calling “the most important educated related Supreme Court case in 50 years,” the U.S. Supreme Court will hold oral arguments in Espinoza v. Montana on January 22. In the case, the plaintiffs are seeking to invalidate, in one fell swoop, thirty-seven state constitutional provisions that say public money may not be used for private religious education.

The plaintiff in the case, Kendra Espinoza, wished to use public funds to send her children to Stillwater Christian School under a 2015 Montana program “to provide parental and student choice in education.” Under the program, scholarships to private schools were financed by private contributions, which were eligible for state-supported tax credits. The Montana Supreme Court, however, struck down the program, citing a state constitutional provision barring the use of state money—in this case, in the form of a tax credit—for religious schools.

Conservatives backed an appeal to the U.S. Supreme Court, arguing that the First Amendment’s right to freely exercise religion prohibits state governments from explicitly refusing to fund religious education. Plaintiffs also claim that the thirty-seven state constitutional provisions barring public money for private school were motivated by anti-Catholic bias. These provisions, Justice Clarence Thomas has written, were “born of bigotry.”

But a distinguished group of legal and religious historians disagree. They write:“The no-funding principle, based on notions of religious liberty and freedom of conscience, arose prior to the rise of significant Catholic parochial schooling and independently of the nativist anti-Catholic movement.” The historians note that the amendments were backed by important insights about the needs of American democracy and the free exercise of religion that predate “either the first significant wave of Irish Catholic immigration or the systematic establishment of Catholic parochial schooling.”

Indeed, long before the advent of wide-scale Catholic immigration, the framers of the Constitution, including Thomas Jefferson and James Madison, opposed funding religious education in Virginia and any efforts that involved compulsory taxpayer support for religion as a violation of religious liberty. Policies should not require taxpayers to fund religious beliefs they do not share, they argued.

Moreover, religion is more freely exercised when it is not entangled with the state. When religious organizations become dependent on government funds, there is a danger they will tailor their views in order to sustain the receipt of public dollars. As education historian Diane Ravitch notes, “Religious liberty is best protected by keeping it separate from government dollars and government control.”

If the U.S. Supreme Court finds for the plaintiffs in this case, it would set a precedent allowing the use of public funds for private religious education, and would without doubt open the floodgates for publicly funded Catholic schools for Catholics, Protestant schools for Protestants, yeshivas for Jews, and madrassas for Muslims.

As our nation becomes increasingly polarized and fractured by race, ethnicity, and class, public education is one of the few remaining unifying forces. Today, we are finally starting to make some important progress—from the halls of Congress to the schools in New York City—on better integrating our public schools by race and class. Forcing states to abandon long-standing provisions that prioritize public funding for public education would represent an enormous step backward.