Nevada Gov. Brian Sandoval has been a strong supporter of the state’s new voucher program. (Kevin Clifford/AP)

The American Civil Liberties Union is challenging the constitutionality of Nevada’s new school voucher program, arguing in a lawsuit filed Thursday that the program violates the state’s prohibition against using public money for religious purposes.

“Parents who want their kids to go to private school are absolutely free to do so,” said Amy Rose, legal director for ACLU of Nevada. “Just not at taxpayer expense.”

The Nevada program, created this year by the state’s Republican-controlled legislature, creates “educational savings accounts” that would allow any parent, regardless of income, to pull a child from the state’s public schools and take tax dollars with them to pay for private or parochial school.

The D.C.-based nonprofit Americans United for Separation of Church and State is joining the ACLU in litigating the case.

Parents could also use the money — an average of $5,100 to $5,700, depending on family income — for transportation, technology or home schooling. Supporters describe it as an escape hatch from poor schools, while opponents say it drains public schools of needed funds.

“What we should be concerned about is fixing the public school system if it is damaged,” Rose said at a news conference Thursday. “I don’t think we should be taking money away from public schools and giving it to private schools.”

The Nevada treasurer’s office is writing regulations to implement the program. A spokeswoman referred a request for comment on the lawsuit to the state attorney general, whose spokeswoman said she could not comment on pending litigation.

But Tim Keller, an attorney for the Institute for Justice — a Virginia-based organization that helped state lawmakers draft the bill that created the Nevada program — vowed to defend the initiative from the ACLU’s “baseless and cynical lawsuit.”

Nevada’s constitution prevents “public funds of any kind or character whatever” from being spent for sectarian purposes. The ACLU argues that such strong language does not allow tax dollars to be used for religious schools, whether or not the dollars pass through parents’ hands first. The organization is seeking an injunction to stop the voucher program from being implemented.

But Keller argued that the program is constitutional because parents are in control of how the money is spent; no money is specifically set aside for religious purposes. “It is precisely the independent decision-making by parents that severs any link between church and state,” Keller said in a statement.

In 2014, Keller’s organization successfully defended Arizona’s educational savings account program, on which Nevada’s was patterned. But Arizona’s constitutional language was different, prohibiting public money from being “appropriated” to support religious establishments. The Arizona Supreme Court ruled that any support of a religious establishment was the result of a parent’s decision, not lawmakers’ appropriation.

Other states increasingly have allowed tax dollars to be used for private school tuition, but most limit the programs to students with disabilities or from low-income families. Nevada’s law is unique because all of the state’s 450,000 K-12 public schoolchildren are eligible to take the money to whatever school they choose.

Conservatives see the breadth of the Nevada program as a political breakthrough, the ultimate in school choice. They are working to spread it nationwide: Lawmakers in Georgia, Iowa and Rhode Island considered similar legislation this year.

Recent court decisions regarding voucher programs in other states show how differently state courts have interpreted their constitutions’ bans on using tax dollars for religious purposes.

In July, the North Carolina Supreme Court upheld a statewide voucher program that provides low-income students with as much as $4,200 a year for private school tuition. But just a few weeks before, the Colorado Supreme Court struck down a voucher program in the state’s third-largest school district, finding the program unconstitutional because it channels public funds to religious schools.

School officials in Colorado have said they are likely to take their case to the U.S. Supreme Court, arguing that state bans on government aid to religious schools violate the U.S. Constitution. They say they would prevail in a case that could have broad implications.

At least 37 states have such provisions in their constitutions; they are known as “Blaine amendments,” after a 19th-century speaker of the U.S. House who proposed a constitutional amendment that would have prohibited states from funding religious educational institutions.