PHOENIX — Public school supporters won a major victory Wednesday in their bid to block Arizona’s massive school voucher expansion law when the state Supreme Court ruled voters could decide the issue in November.

The high court’s decision was also a major loss for Republican Gov. Doug Ducey, Republican state lawmakers and school choice supporters in Arizona and nationally who backed the proposal, the largest expansion of school vouchers in the U.S. Nevada has a similar law but it isn’t funded so is unused.

The Arizona law would allow all parents to use public money to send their children to private or religious school, with a cap on enrollment at 30,000 students.

Barring a repeal or replacement by the Legislature, the measure expanding the existing voucher program to all students will be on the November ballot.

Arizona’s Constitution allows voters to block a new law by circulating petitions, and if enough signatures are collected the law “referred to the voters” and put on hold until the next general election. Parents and teachers who opposed the new law because they believed it siphons cash from Arizona’s already-underfunded public schools hit the streets last summer in an all-volunteer effort and collected more than 110,000 signatures to put the law on hold.

Wednesday’s ruling means will voters decide whether to strike down the voucher law, which is backed by school choice group American Federation for Children, formerly led by now-Education Secretary Betsy DeVos.

The spokeswoman for Save Our Schools Arizona, the group that succeeded in blocking the law, said any effort to block the vote would be beaten back.

“If they attempt a replacement we will refer it,” Dawn Penich-Thacker said. “We will pound the pavement and collect signatures yet again, and this time we’ll do it better and faster and get more of them, because we know what we’re doing.

“If they repeal it we will pivot to the larger issues, which is education funding in general,” she said. “The reason these vouchers are a problem is because the public education system is starving.”

Ducey’s spokesman had no comment. Republican House Speaker J.D. Mesnard said the Legislature could do nothing and allow the voters to decide, replace it with another version or outright repeal, which he called “very unlikely.”

“There are folks on both sides that feel passionately about the issue, and you’d just be undoing everything,” Mesnard said. “I think the folks who wanted to see it moved forward would like either to do it a better version of the bill or just allowing this one to go forward at the ballot.”

The state Supreme Court upheld a lower court judge who said voucher supporters didn’t have a right to sue because the Legislature removed that in 2015 before restoring it during last year’s legislative session.

The voucher law was a major priority of Ducey and was backed by school choice group American Federation for Children, formerly led by now-Education Secretary Betsy DeVos.

The attorney for the American Federation for Children, which backed the court challenge, said the petitions gathered by the group Save Our Schools Arizona “all had a fatal flaw” and alleged widespread fraud.

“The parents who needed an ESA for their child deserve their day in court, but the Supreme Court has denied it,” attorney Tim La Sota said in a statement. “It’s unfortunate that these facts will not be heard in court for the sake of the parents who are being blocked by the unlawful referendum efforts. And again our Supreme Court has been unable to fashion a consistent body of law to apply to ballot measures equally whether they are liberal or conservative.”

Technically called Empowerment Scholarship Accounts, the Arizona program allows parents to take between 90 percent and 100 percent of the state money a local public school would receive to pay for private or religious education. The average student who isn’t disabled currently receives about $6,000 a year to pay for tuition or other costs, while disabled students get about $20,000.

The 2017 expansion expands eligibility to all students by 2022 but caps enrollment at about 30,000.

Supporters say vouchers give parents more choice. Opponents argue they siphon money from public schools.