The U.S. Supreme Court narrowly endorsed school vouchers yesterday, upholding a Cleveland program that provides grants to low-income parents to help pay for their children's enrollment in parochial schools.

The court ruled 5-4 that the Ohio voucher law does not violate the Constitution's ban on state sponsorship of religion because it mandates that students have a choice between private academies, church-run schools or public schools that perform better.

The decision could foster major changes in public education. Other states have waited to see whether vouchers pass muster before considering programs of their own. And President Bush has asked Congress to fund vouchers as a means of improving education in America.

"This decision clears the way for other innovative school choice programs," Bush said. "I urge Congress to move quickly to build on the momentum generated from this decision to enact my education priorities."

The ruling is the latest in a series of major court rulings decided by a single vote. In a 21-page opinion, Chief Justice William H. Rehnquist sought to refute dissenters point by point, saying that Cleveland's program does not violate the constitution's prohibition of state-sponsored religion.

"No reasonable observer," he wrote, "would think a neutral program of private choice, where state aid reaches religious schools solely as a result of the numerous independent decisions of private individuals, carries with it the imprimatur of government endorsement."

But in a strongly worded dissent that took aim at each of Rehnquist's arguments, Justice David H. Souter said the majority had "betrayed" decades of precedent that barred state support of a particular religion.

"The scale of aid to religious schools approved today is unprecedented, both in the number of dollars and in the proportion of systemic school expenditure supported," he wrote.

"Whenever we remove a brick from the wall that was designed to separate religion and government, we increase the risk of religious strife and weaken the foundation of our democracy," said Justice John Paul Stevens in a separate dissent.

In practical terms, the decision shifts the battle over school vouchers from the courts to state legislatures. Florida and Wisconsin already have voucher programs. In Maryland, the voucher fight could start soon, as Roman Catholic leaders said they would lobby for vouchers, which could benefit 70,000 students in the state's parochial schools. But the state teachers union said it would resist, and reform proposals have not fared well in Annapolis.

"I honestly do not think it will have much of an impact in Maryland," said state Superintendent Nancy S. Grasmick. "We already have a process for dealing with failing schools, and there has not been a lot of interest in the General Assembly."

For more than a decade, high court rulings have been lowering the wall between church and state. An earlier decision allowed parents sending children to religious schools to deduct from taxes the cost of tuition, textbooks and transportation.

At the heart of the cases is a First Amendment provision known as the Establishment Clause, which bars the government from making "any law respecting an establishment of religion."

Critics say the 6-year-old Cleveland program, which provides mostly low-income families with up to $2,250 for private school tuition, does just that because most of the private institutions that participate are affiliated with a church. And nearly 97 percent of the more than 3,700 children involved in the program enrolled in parochial schools.

However, Rehnquist said the Cleveland program is constitutional because parents chose to enroll their children in parochial schools and they had other choices, such as magnet or charter schools, or Saturday tutorials at regular public schools.

"The constitutionality of a neutral educational aid program," he wrote, "simply does not turn on whether and why, in a particular area, at a particular time, most private schools are run by religious organizations, or most recipients choose to use the aid at a religious school."

Justice Sandra Day O'Connor, widely considered the swing vote, emphasized in a concurring opinion that far more students took advantage of options other than religious schools. Joining the majority were Justices Antonin Scalia, Anthony M. Kennedy and Clarence Thomas.

The dissenters said the conservative majority had "read away" the separation of church and state. Souter, who read his dissent from the bench, predicted sectarian conflict, saying that members of different religions would now fight over the provision of government money to parochial schools and the teachings in those schools.

"Just how is the state to resolve the resulting controversies," he wrote, "without provoking legitimate fears of the kinds of religious favoritism that, in so religiously diverse a nation, threaten social dissension?"

Also dissenting were Justices Ruth Bader Ginsburg and Stephen G. Breyer.

Voucher supporters hailed the ruling as a boon for education, particularly for underprivileged urban youths in poorly performing public schools. Such students can now choose a better school, supporters said, and public schools will be forced to improve.

Opponents described vouchers as bad public policy that will only weaken public schools attended by the vast majority of children. The tuition grants, opponents said, will divert valuable public money away from resource-starved public schools.

In Maryland, Ronald J. Valenti, superintendent of the Archdiocese of Baltimore's schools, said yesterday's decision will prompt efforts to get a voucher program here.

"We will see whether [legislators] will continue to avoid the plight of poor kids in bad schools," said Dick Dowling, executive director of the Maryland Catholic Conference.

Patricia A. Foerster, president of the Maryland State Teachers Association, said religious leaders should avoid a legislative fight if they want to improve education for all children.

"Public schools are where public funds should be spent," Foerster said, "and we will continue to fight for public schools and the needs of the majority" of students.

In Cleveland, the decision is expected to result in the growth of the voucher program.

"Now that this decision has come down in such a broad endorsement," said Ohio Attorney General Betty Montgomery, who litigated the case, "I expect we will have an expansion and more creative use of the voucher program in Ohio."

Roberta Kitchen, a Cleveland mother who sends her 11-year- old daughter to a nearby Lutheran school, favors expansion of the program to cover her four older children who attend private schools.

"If they had remained in the public schools, they would have joined the statistics of their peers who are dropouts because they weren't challenged in the schools and there was nothing there for them," Kitchen said.