BANGOR, Maine (AP) — Maine families who want to send their children to religious schools at taxpayers' expense have filed suit in federal court.

Two national conservative groups that have brought forward religious freedom cases in other states are representing three families that filed a federal lawsuit in Bangor on Tuesday. The families ask the courts to require local communities to pay for tuition at religious schools, while also declaring Maine's school tuition program unconstitutional.

"I hope the courts will decide that it's unconstitutional to discriminate against someone based on their religion," said plaintiff Alan Gillis, of Orrington, who sends his 16-year-old daughter to a Christian school in Bangor. He added: "There have been recent decisions at the Supreme Court that have ruled in favor of religious freedom, so we hope the judicial environment will be favorable for us."

Maine communities without their own schools must either contract with public or private schools, or pay tuition at a school of the parents' choice. The tuition program dates to the 1870s, according to Institute for Justice attorney Tim Keller, who's representing the families, along with First Liberty Institute.

By 1979, over 330 students were attending religious schools at public expense.

But a 1980 legal opinion by Maine's attorney general advised that it's unconstitutional to use public funds to send students to schools "characterized by a pervasively religious atmosphere." By 1982, lawmakers changed state law to prevent religious schools from receiving such tuition payments.

The suit says none of the families have asked for tuition payments for religious schools because such requests would be "futile." Keller's group, the Institute for Justice, is currently challenging Montana's exclusion of religious schools from a state private school scholarship program.

His group also helped defend parents who won a 2002 U.S. Supreme Court decision ruling that a Cleveland, Ohio, school voucher program was constitutional, even though parents could choose to send their children to religious schools.

"To date, the courts have agreed it's unconstitutional to discriminate against school who desire religious education," Keller said.

Maine's Department of Education declined comment through a spokeswoman.