Three families are suing the commissioner of the Maine Department of Education over the state policy barring tuition reimbursements for religious schools.

The lawsuit filed Tuesday in U.S. District Court in Bangor challenges a decades-old law in Maine. Local school administrative units that do not have their own secondary schools can pay a certain amount in tuition for students to go to outside public or private schools. But that money cannot be used for religious schools, a policy that the complaint calls discriminatory and unconstitutional.

The plaintiffs, all parents with children in central Maine, are represented by two national groups that advocate for religious liberty and school choice. The lawsuit comes at a time when the Trump administration has made the push for alternatives to public schools central to the national education policy debate.

“In the state of Maine, a victory in this case would allow any family who lives in a town that tuitions students to public or private schools to choose religious options,” said Tim Keller, a senior attorney at the Virginia-based Institute for Justice.

A spokeswoman for the Maine Department of Education declined to comment on the case.

More than 30 states have constitutional amendments that prohibit state funding of religious organizations, including schools. Though Maine is not one of them, it passed a law in 1981 that bars public funding to sectarian schools. Legislative efforts to expand school choice and give taxpayer money to religious schools have failed to gain traction in recent years.

This is the third time the Institute for Justice has filed a legal challenge in Maine over this issue. The law firm took similar cases in 1997 and 2002, losing both times.

Keller said the group decided to try again in light of a U.S. Supreme Court ruling last year. In that case, Trinity Lutheran Church in Missouri was barred from participating in a state program that reimburses the cost of rubberizing playground surfaces. The nation’s highest court ultimately decided the church should be eligible for that public funding. To advocates for school choice, it was an opening.

“That was our cue to try one more time in Maine,” Keller said.

The group joined with the Texas-based First Liberty Institute to represent the three sets of parents, including Troy and Angela Nelson of Palermo, a town northeast of Augusta with roughly 1,500 residents. Troy Nelson is a farmer, and Angela Nelson works in local government. Palermo is part of Regional School Unit 12, which does not have its own public high school. Parents can choose where to send their children after eighth grade, and the RSU pays up to a certain amount of tuition for that school. The majority of Palermo teenagers go to Erskine Academy, a secular private school in South China, where the approved tuition rate for the 2015-16 school year was more than $10,000.

The Nelsons’ daughter, Alicia, soon will begin her sophomore year at Erskine Academy, and the Nelsons receive the tuition reimbursement that pays for her education. But their son, R.J., is headed into seventh grade at Temple Academy, a private Christian school in Waterville, and the cost of his education will be entirely on them during his high school years. It is not clear what the tuition is for either school, and a request for comment from Temple Academy was not returned Tuesday.

“It’s a financial burden,” Troy Nelson said. “We live modest, conservative lives. I’d love to be driving the new vehicles like everybody else, but I choose to give my son a good education.”

Nelson, 45, graduated from Erskine Academy and considers it a good school. But he said he likes the discipline at Temple and wishes he could send both of his children there.

“I talk to a lot of parents that want to send their kids to do something different, and they just can’t swing it,” he said.

Nelson predicted his children would graduate before the case was resolved.

“I’m doing this not for my kids, but for kids down the road,” he said.

The other plaintiffs live in Glenburn and Orrington, and both families have children who attend Bangor Christian Schools. If the lawsuit is successful, it would not affect districts that contract to send all of their students to outside high schools as a group. It is not clear how many students live in districts that reimburse their parents for tuition at the high school of their choice. Keller said the Institute for Justice has identified a handful of districts with that policy, mostly in Penobscot, Kennebec and Lincoln counties.

Angela and Troy Nelson, with their children, R.J. and Alicia, are plaintiffs in a lawsuit to allow the state to pay tuition to religious schools.