By Andrew Chung

(Reuters) -The U.S. Supreme Court on Friday took up a challenge by two families with children attending Christian schools to a Maine tuition assistance program that bars taxpayer money from being used to pay for religious educational institutions in a case that could further narrow the separation of church and state.

The justices agreed to hear an appeal by the families of a lower court ruling in favor of the state that concluded that Maine’s program did not violate the U.S. Constitution’s First Amendment right to the free exercise of religion.

The case is the latest one for the court that pits the free exercise of religion against another element of the First Amendment: the separation of church and state that prohibits government establishment of an official religion or favoring one religion over another.

Some sparsely populated areas of Maine lack public secondary schools, so state law allows public funds to be used to pay for tuition at certain private schools of a parent’s choice as long as they are “nonsectarian.”

The case involves two sets of parents – David and Amy Carson, and Troy and Angela Nelson – who sued the state in 2018 in federal court, arguing that by the tuition assistance program’s exclusion of religious schools discriminates against them based on religion.

The Carsons pay out of pocket to send their daughter to Bangor Christian Schools in Maine’s third-largest city. The Nelsons would like to send both of their children to a Christian school called Temple Academy in Waterville, Maine, but can afford the tuition for only one, so their son attends Temple Academy while their daughter does not.

The schools, both of which are private and nonprofit, describe themselves as seeking to instill a “Biblical worldview” in their students. Bangor Christian Schools does not hire teachers who are gay or transgender, and would potentially expel openly gay or transgender students, according to court papers. Temple Academy does not hire gay teachers and likely would not accept gay, transgender or non-Christian students, court papers said.

The families contended that they are entitled to tuition help given the U.S. Supreme Court’s recent rulings siding with religiously based institutions, including its decision last year endorsing Montana tax credits that can help pay for students to attend religious schools. The families are represented by the Institute for Justice conservative legal group.

The Boston-based 1st U.S. Circuit Court of Appeals ruled against the families last year, deciding that Supreme Court precedents did not forbid states from barring public funds from religious entities based on how those dollars would be used.

While states cannot disqualify religious schools from public aid programs simply because of their religious status or affiliation, Maine is not required to subsidize schools that would use the money to provide religious instruction, the 1st Circuit decided.

The families appealed to the Supreme Court, whose conservative majority has taken an expansive view of religious rights.

“States should not be permitted to withhold an otherwise available education benefit simply because a student would make the private and independent choice to use that benefit to procure an education that includes religious instruction,” they said in a court filing.

Maine Attorney General Aaron Frey, defending the law, said in a court filing that religious schools willing to provide a secular education may receive public funds.

“In excluding sectarian schools, Maine is declining to fund explicitly religious activity that is inconsistent with a free public education,” Frey wrote.

(Reporting by Andrew Chung in New York; Editing by Will Dunham)