The Florida Supreme Court yesterday declared unconstitutional a school voucher program central to Governor Bush’s education reform effort, leaving tens of thousands of children with fewer options to escape failing schools.

In a 5-2 decision, the court found that the Florida Constitution’s guarantee of a “uniform” system of public education precluded the voucher program, which allows students at schools deemed to be failing to take their government-provided funding to a private school.

“The Constitution prohibits the state from using public monies to fund a private alternative to the public school system,” the court’s chief justice, Barbara Pariente, wrote for the majority. “The provision mandates that the state’s obligation is to provide for the education of Florida’s children, specifies that the manner of fulfilling this obligation is by providing a uniform, high quality system of free public education, and does not authorize additional equivalent alternatives.”

The dissenting judges accused the majority of, in essence, inventing a restriction that appears nowhere in the Constitution. “It does not preclude the legislature from using its general legislative power to provide a private school scholarship to a finite number of parents who have a child in one of Florida’s relatively few ‘failing’ public schools,” Judge Kenneth Bell wrote. He noted that the constitutions of 10 states expressly prohibit public funding for private schools, but Florida has no such explicit ban.

Mr. Bush, who pushed the “opportunity scholarships” into law in 1999, disputed the court’s contention that the program undermines public schools.

“The public never benefits from the government protecting a monopoly,” the governor said in a written statement. “The purpose of the opportunity scholarship program is to improve public education and stimulate competition. The court’s decision today is a blow to educational reform.”

Supporters of school voucher programs condemned the ruling as a judicial intrusion on the prerogatives of the legislature and the governor. “This is judicial activism at its worst,” a Manhattan Institute scholar and professor at the University of Arkansas, Jay Greene, said. “They invented this out of whole cloth.”

As of November, only 733 students were enrolled in private schools under the program. However, Mr. Greene insisted that the initiative encouraged public schools across Florida to boost their performance to avoid losing money for students who opted to take the scholarships. “The program is incredibly tiny, but its benefits are not primarily for those 700 students. The removal of the voucher sanction may undermine the motivation that these public schools have for improvement,” the professor said.

One of the attorneys who challenged the voucher program, Ronald Meyer, said he was “very pleased” with the ruling. “The answer to fixing problems within the public school setting was not taking money away from public schools,” he said. “I’m hopeful this will be a catalyst for focusing attention back on public schools.”

Mr. Meyer said the litigation was funded by two public school teachers’ groups, the National Education Association and the Florida Education Association. He also noted that part of Mr. Bush’s education initiative that allows students at failing schools to transfer to other public schools remains intact.

A political science professor at the University of South Florida, Susan McManus, said Mr. Bush would be wounded by the court’s action striking down the voucher program. “It’s been a big priority of Jeb Bush, no question about it. It’s been one of the centerpieces of his education reformation,” she said.

Ms. McManus said she expected that Mr. Bush, who is leaving office at the end of the year, might try to find a legislative fix to the program, but would not try to press for a constitutional amendment or seek to oust the judges who scuttled the program. “The Republicans in Florida have not gotten very far with attacking the Florida court system,” she said. “They’ve caught a lot of flak. I can’t imagine one newspaper in this entire state endorsing them doing that.”

Still, the professor said the decision is likely to affect the governor’s race, where a leading Republican candidate is the state’s attorney general, Charlie Crist, who defended the voucher program in court. “Any doubt that this would be a key issue in the campaign has just been tossed out the window,” Ms. McManus said.

Advocates on both sides of the case said the impact of the decision outside of Florida appeared to be limited because the ruling turned on the idiosyncrasies of that state’s constitution. For the same reason, the decision is unlikely to be overturned by the U.S. Supreme Court. Mr. Greene said of the Florida justices, “They devilishly chose the one basis of ending the program that would not be easy to appeal in federal court.”

A lawyer with the American Jewish Congress, which backed the challenge to the voucher program, said the court’s ruling would be of some help to critics of vouchers because it noted that the relatively low tuition at parochial and sectarian schools is due in large part to the fact they are exempt from many of the rules that apply to public schools. “It does pick up on an argument that opponents of vouchers have made for some time that the claims of lower costs for religious schools are in part a function of the regulatory playing field,” the attorney, Marc Stern, said.

Some earlier court rulings struck down the program as an illegal subsidy to religious schools, but yesterday’s decision did not rest on that ground. Mr. Stern said aides to Mr. Bush warned Jewish groups that if the school voucher program was shut down on that basis, Jewish-run nursing homes might lose state funding as well.

While ordering the voucher program for students in failing schools terminated at the end of this year, the Florida court carefully avoided disturbing a much larger and older program under which roughly 16,000 handicapped and learning disabled students use public funds to attend private schools. In dissent, Judge Bell called the distinction “nonsensical.”

An attorney who represented recipients of the vouchers, Clark Neily, called the court’s opinion “atrocious” and “outrageous.” Mr. Neily, who works for a libertarian legal group, the Institute for Justice, said a few other states have similar constitutional provisions calling for uniformity in public education. In 1992, the Wisconsin Supreme Court found similar language was no bar to a voucher program in Milwaukee.

Mr. Neily called the Florida court’s decision “one of the most blatant examples I’ve seen in a long time of results-oriented reasoning.” The five judges who voted to strike down the program were Democrats; the two dissenters were Republicans.