Critics of two new state voucher programs for foster and disabled children attending private schools filed a lawsuit Tuesday asking the Arizona Supreme Court to declare the grant programs unconstitutional.

The lawsuit filed by the American Civil Liberties Union of Arizona and People for the American Way and three individuals contends that the programs the first voucher programs enacted in Arizona violate state constitutional prohibitions against state funding for private or religious school.

The lawsuit asked the Supreme Court to prohibit implementation of the programs, but not until the 2007-2008 school year to avoid harming people who relied on the programs in good faith.

"A prompt decision is important," said Don Peters, a lawyer for the challengers.

The challengers said their lawsuit has backing from numerous public education groups, and one of the individuals who was a named plaintiff in the suit is a member of the Madison Elementary School Districts' governing board.

"Vouchers drain money from public schools that don't have enough money as it is," said the board member, Scott Holcomb. "These statutes would open the door to wholesale funding of private education with public dollars."

When the programs were enacted, supporters called them a step toward increasing educational opportunities for parents and their children.

The voucher program for disabled students has taken effect, while the one for foster children is to be launched with the 2007-2008 school year, said Tim Keller, an attorney for the Institute for Justice.

The institute supports school-choice programs and plans to ask the Supreme Court to let it intervene on behalf of individual families to defend the programs.

A key legal issue in the case will be whether the court finds that the beneficiaries are the children or the schools, said Keller. "The beneficiary are these children children who are particularly vulnerable in their education needs."

The lawsuit is the second filed this fall against school-choice measures enacted by the Legislature earlier this year.

In September, the ACLU and the Arizona School Boards Association filed a lawsuit in Maricopa County Superior Court to challenge a new state corporate income tax break for business donations for private grants for private school tuition.

The state already has an income tax credit for individuals who donates to private school scholarship groups, and the Arizona Supreme Court upheld that credit in 1999.

The state high court said in its 1999 ruling that the individual income tax credit did not violate the prohibition against state funding of private or religious education, largely because the dollars involved were donated by the individuals and never reached the state treasury.

Keller noted that the Supreme Court's entire membership has turned over since the 1999 ruling.

The corporate income tax credit and the two voucher programs were approved by the Republican-led Legislature with the reluctant acquiescence of Democratic Gov. Janet Napolitano, a critic of vouchers and the two tax credits.

The Attorney General's Office will defend the law's constitutionality in court, spokeswoman Andrea Esquer said.

State Superintendent of Public Instruction Tom Horne, who with the state treasurer was one of two named defendants in the suit, acknowledged Tuesday that he'd said previously that vouchers would violate the Arizona Constitution.

However, Horne said he hadn't reviewed the two specific laws being challenged by the lawsuit and had no opinion on whether they were constitutional.

Napolitano said June 28 that it was an "open question" whether the voucher programs would survive a legal challenge.