A lawsuit over public funding for Maine religious schools is headed for a federal appeals court in Boston.

Local school administrative units that do not have their own secondary schools can pay a certain amount in tuition for students to attend outside public or private schools, but Maine law does not allow for that money to be used at religious schools. So three families sued the state last year to get that tuition reimbursement for their children at Bangor Christian School in Bangor and Temple Academy in Waterville.

District Judge D. Brock Hornby heard oral arguments in the case Monday in U.S. District Court in Portland. He issued a ruling Wednesday that upheld the law. But the judge did not issue a definitive opinion about a central argument in the lawsuit, saying that will be decided by higher courts.

“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,” Hornby wrote. “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).”

The plaintiffs relied on a 2017 U.S. Supreme Court case about whether a state could bar a church preschool from a public program that paid to rubberize playground surfaces. In that case, the Supreme Court decided in favor of the church, but with the distinction that their decision did not address religious uses for funding.

Hornby said that case did not clearly upend case law that bars public money from going to religious education, and that the appeals court would need to address that issue.

He also cited the Maine Human Rights Act, which prohibits religious groups from receiving public money if they maintain a discriminatory hiring policy against LGBTQ people. Both Bangor Christian and Temple Academy do so, according to court documents.

The case has attracted interest from civil and religious liberties groups, education leaders and the U.S. Department of Justice, which supports the plaintiffs.

Tim Keller, a senior attorney from the Virginia-based Institute for Justice, represented the plaintiffs. He said the organization would immediately appeal the decision and take the case to the U.S. Supreme Court if necessary.

“Today’s decision is disappointing but not unexpected,” Keller said in a statement. “District judges are generally required to uphold previous rulings from higher courts and we expected that, no matter the decision, this important case was going to be appealed. We are grateful that Judge Hornby moved quickly to issue a ruling just two days after the hearing. This fight against religious discrimination is headed to the First Circuit and then possibly to the Supreme Court.”

The statement also included a comment from one of the plaintiff parents.

“We’re disappointed that today’s ruling did not end Maine’s discrimination against religious schools,” said Judy Gillis, who lives in Orrington and has a daughter at Bangor Christian. “However, we are waging this fight not only for our own daughter, but for every family that wants to send their son or daughter to the school that works best for them. We look forward to the appeals court hearing our case.”

Zachary Heiden, legal director for the ACLU of Maine, said this is the fifth time a court has upheld the tuition law. The judge allowed the civil liberties group to file an amicus brief and participate in oral arguments on the case this week.

“It is not the state’s job to teach children how to pray or how to practice religion, but it is the state’s job to avoid funding entities that promote discrimination,” Heiden wrote in an email. “This case will almost certainly be appealed. On appeal, we expect the court to agree with its prior ruling that Maine’s tuition law is constitutional.”

“Nothing about that law has changed, and nothing about the First Amendment has changed, since the last case. No religious school has joined in this case, presumably because they do not actually want to come under the supervision of the Maine Department of Education and the Maine Human Rights Commission.”

The Maine Attorney General’s Office represented the state at oral arguments, but a spokesperson did not respond to an email request for comment Thursday.

The parents filed the lawsuit in August.

Local school administrative units that do not have their own secondary schools can pay a certain amount in tuition for students to attend outside public or private schools. But under Maine law that money cannot be used at religious schools, a policy that the families’ lawsuit calls discriminatory and unconstitutional.

If the lawsuit is successful, it would not affect districts that contract to send all their students to outside high schools as a group. It is not clear how many students live in districts that reimburse parents for tuition at the high school of their choice. Keller has said the Institute for Justice has identified a handful of districts in Maine with that policy, mostly in Penobscot, Kennebec and Lincoln counties.