The U.S. Supreme Court signaled it is poised to strengthen the rights of parents to use public dollars to pay tuition at faith-based schools.

Hearing arguments Wednesday in Washington, the court's conservatives cast doubt on a Maine program that covers the cost of private education in parts of the state that don't have public schools but bars use of the funds at schools that promote religion.

Chief Justice John Roberts Jr. and Justice Samuel Alito said the state was discriminating on the basis of religious beliefs. Justice Brett Kavanaugh said two families challenging the exclusion of religious schools "are seeking equal treatment, not special treatment."

The case gives school-choice advocates a chance to reinforce a line of Supreme Court rulings that have backed voucher programs and, to at least some degree, required states to include religious schools.

The families say the Maine policy violates the Constitution's free exercise clause because it forces them to choose between a public benefit and their religious rights.

Under the program, areas that lack their own public schools can contract with nearby institutions to send students there or instead can pay tuition at a public or approved private school chosen by the parents. State policy requires the private schools to be nonsectarian, meaning they don't teach through the lens of a particular faith.

The families are seeking to extend rulings favoring the use of taxpayer funds to pay religious school tuition. In 2002, a 5-4 court ruled that voucher programs don't violate the constitutional separation of church and state even if most of the money goes to religious schools. In 2020, the court in 2020 voted 5-4 to reinstate a Montana scholarship program used primarily to send children to religious schools.

Maine says its program is distinct from those the court reviewed in previous cases. The state says its system is a means of providing a public education in sparsely populated areas, not an effort to subsidize private schooling.

Of the state's 180,000 school-age children, about 4,500 attend private schools chosen by the parents. That number represents the vast majority at 11 schools known colloquially as "town academies."

Maine says it and Vermont are the only states that use private schools in place of public schools, rather than as an alternative under a school-choice program.

A federal appeals court said the Maine program was constitutional because it excludes schools based on the material they teach, rather than on their status as religious institutions. Although the Supreme Court has relied on that so-called use/status distinction in past cases, religious-rights advocates say it lacks any constitutional basis and should be discarded.

The program is being challenged by David and Amy Carson, who say they are entitled to tuition assistance for sending their daughter to Bangor Christian School, and Troy and Angela Nelson, who say they haven't been able to afford to send their children to Temple Academy, another religious school.

The case is Carson v. Makin, 20-1088.

Greg Stohr reports for Bloomberg News.

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