The U.S. Supreme Court on Wednesday will hear a legal challenge from Maine that could have a national impact on school choice.

Maine allows students in towns with no public high schools to put taxpayer money toward the cost of an outside school, public or private. But the law bars them from using those funds at religious schools. The families who filed this lawsuit want to do away with that rule.

The program has survived four previous challenges, but none reached the nation’s highest court. The conservative shift on the Supreme Court could give these plaintiffs a greater chance at success, and the case has attracted more than three dozen briefs from national groups on both sides of the issue.

If the justices overturn the law, the direct impact would likely be limited. It applies to a relatively small number of Maine students who live in school administrative units that do not have public high schools. The only state with a comparable law is Vermont.

But the indirect impact could be significant. Legal experts said the ruling could either put a damper on or bolster school choice programs that seek to use public funds for religious options.

“The implications are national in scope,” said John Maddaus, an associate professor emeritus at the University of Maine Orono.

Maine has 260 school administrative units serving nearly 180,000 students from kindergarten to 12th grade. More than half do not have their own secondary schools, and many sign contracts or make agreements with other schools to provide those services. The law says SAUs that do not have public high schools can pay outside public or private schools to accept their students, so long as those schools aren’t “sectarian.” An SAU can pay up to the statewide average tuition rate – $11,275 last year — and the balance is the parents’ responsibility.

More than 4,500 students attended private schools through a contract or the tuition program during the 2017-2018 year, according to court documents. The state says nearly all attended one of 11 private schools known as “town academies,” like Thornton Academy in Saco. Another 208 students are receiving public funding at other private schools this year, a Maine Department of Education spokeswoman said on Tuesday. It is not clear how many students in Maine attend religious schools at their own expense, or how many would do so if the court overturned the current law and they could use state tuition money.

The Maine Attorney General’s Office has argued that this program helps the state meet its obligation to provide free public education to all students. The state also has said the First Amendment doesn’t require the government to subsidize religious education.

“While typically a public education would be provided through public schools, the lack of public schools in some parts of Maine means that this (is) not always possible,” Attorney General Aaron Frey wrote in the state’s brief. “So, a small number of children are eligible to attend an approved private school of their choosing at public expense. This is not a voucher, scholarship, or subsidy program. Rather, it is simply a method to deliver a free public education. And because Maine is using private schools as part of its public education system, schools that promote a particular religion or present material through a religious lens are not eligible. The education provided in such sectarian schools is simply not comparable to a public education.”

In this case, three families filed a federal lawsuit in 2018. One is no longer involved in the litigation. The plaintiffs are represented by the Institute for Justice, a national law firm that takes cases on religious liberty and school choice. The same group has been involved in previous challenges to Maine’s law.

They decided to try again in light of a 2017 Supreme Court decision. In that case, Missouri barred a church from participating in a state program that reimbursed the cost of rubberizing playground surfaces. The court ruled that religious organizations cannot be excluded from state programs if they have secular intent, and Missouri had discriminated against this church based solely on its religious status.

Last year, while the lawsuit from Maine was pending, the Supreme Court issued another opinion that is likely to be important to the arguments on Wednesday. The court considered a scholarship program in Montana that provides tax credits for donations to private scholarship organizations. When the state said those scholarships could not be used at religious schools, parents sued. The justices ultimately said the state could not exclude religious schools.

The plaintiffs in the Maine case have said the state’s law violates their constitutional right to exercise their religion.

“Maine’s sectarian exclusion discriminates against families who are eligible for the tuition assistance program and believe that a religious education is the best option for their child,” their attorneys wrote in their brief. “The exclusion forces such families to choose between a public benefit to which they are entitled and their right to send their child to a religious school.”

David and Amy Carson live in Glenburn and met when they were students at Bangor Christian Schools. David Carson is a general contractor, and Amy Carson helps run the business. When it was time for their only daughter to start kindergarten, they enrolled her at Bangor Christian Schools as well. Their town doesn’t have a public high school, so they could have used the tuition program to send their daughter to John Bapst Memorial High School in Bangor or another approved school. But they chose to keep her at Bangor Christian Schools. Olivia Carson, now 19, graduated this year, and is a business student at Husson University.

Amy Carson said her daughter excelled in a small class of two dozen, and the family valued the Bible classes that were part of the school routine. Because their daughter has graduated, the family will no longer qualify for the tuition reimbursement if the Supreme Court overturns the law. But Amy Carson said the family signed onto the lawsuit anyway because she knows there are other families who could not afford to make the same choices. She estimated they spent more than $20,000 on tuition over the four years of high school.

“It would have been great to have the benefit while she was in high school,” Amy Carson, 45, said. “But we look at all the other families that would benefit from it, whether it would be somebody right down the road from me or in another town.”

Maddaus, the associate professor emeritus at UMaine, researched the state program in the 1980s and 1990s, and his writing is cited in the briefs in this case. If the court overturns the law, he said some families might enroll their children in religious schools for the first time or move to SAUs that would then be required to pay tuition at religious schools.

“It’s certainly possible that it will have some implications in Maine in terms of an increase in the number of students who are enrolled through town tuitioning,” Maddaus said.

Arif Panju, a managing attorney at the Institute for Justice, said multiple states expanded their school choice programs in light of the Supreme Court’s ruling on the Montana case. His organization represented those plaintiffs.

“You’ve got tons of families waiting for more educational options,” he said.

The principal of Bangor Christian Schools said Tuesday that she would not comment on the case. The superintendent of another school mentioned in the lawsuit, Temple Academy in Waterville, did not return a message Tuesday. The state said those two schools discriminate against teachers and students based on sexual orientation and gender identity, so they would be forced to change those policies or reject public funds even if a Supreme Court ruling meant that religious schools had to be included in the tuition program.

Kimberly Wehle, a professor at the University of Baltimore School of Law, said she is concerned the court could endorse such discriminatory policies by overturning Maine’s law. The ruling could show how far the conservative majority will shift the precedent on the separation of church and state, she said.

“I think Maine was chosen as a test balloon to try to constitutionalize discrimination on the basis of other characteristics as a matter of the free exercise of religion,” Wehle said.

The U.S. District Court of Maine and the 1st U.S. Circuit Court of Appeals in Boston both found Maine’s tuition program to be constitutional. More than two years ago, the first ruling in the case foreshadowed its national importance.

“It has always been apparent that, whatever my decision, this case is destined to go to the First Circuit on appeal, maybe even to the Supreme Court,” U.S. District Judge D. Brock Hornby wrote in June 2019. “I congratulate (the parties) on their written and oral arguments in this court. I hope that the rehearsal has given them good preparation for the First Circuit (and maybe even higher).”

Oral arguments in Carson v. Makin will begin at 10 a.m. Wednesday and will be streamed live on the Supreme Court website. A decision is not expected until next year.