The landscape of American education may be starkly different after the Supreme Court rules on whether school vouchers give parents the freedom to choose what kind of schooling their children get, or violate the Constitution by mixing church and state.

The High Court heard arguments for and against the controversial Cleveland school voucher program Wednesday. The court's answer, expected anytime before the end of its 2001-2002 term in June, could remap the educational landscape.

Numerous states and school districts are awaiting word from the high court about whether there is a way to set up a voucher program that does not violate the constitutional principle of separation of church and state.

The justices were notably intense in their lively grilling of the attorneys presenting both sides of the case, with their questions indicating that the real-world consequences of their ruling would be a major factor in their decision.

One result the justices seemed concerned about was whether the school voucher setups, like the one in Cleveland, would treat all children and parents fairly.

That had been the stated purpose of the 6-year-old program, in which parents can use tax funds of up to $2,250 per year to send their kids to public, private or religious schools teaching kindergarten to eighth grade. The program was geared toward poorer families, with about 60 percent of the 3,800 voucher-using students in the 1999-2000 school year living at the poverty line or lower.

But some balked at the program when they learned that an astounding 96 percent of students enrolled in the program were using them for parochial schools, and that only nine of the participating 51 schools are nonreligious.

The voucher amounts nearly cover the cost of a church-subsidized education, but do not begin to cover normal tuition at many secular academies. That, they said, amounts to de facto state funding of religion.

Secular private schools and suburban public schools are eligible to participate in the program, and the fact that more have not done so is no fault of the voucher program itself, Ohio Assistant Attorney General Judith French argued to the court.

The numbers don't look so skewed when you consider that parents have other choices aside from vouchers, including sending their children to charter or magnet schools, Justice Sandra Day O'Connor said.

"Why should we not look at all the options open to the parents in having their children educated?" she asked.

Whether or not that is true is at the heart of the matter, Justice Anthony M. Kennedy told a lawyer, arguing that the voucher program is unconstitutional Wednesday.

"The question is whether there is neutrality" between religious and nonreligious schools, he said.

Chief Justice William H. Rehnquist and Justice Antonin Scalia seemed sympathetic to Ohio's argument that something must be done to help children trapped in a public school system whose quality has been heavily criticized over recent years - in the 1998-1999 school year, the Cleveland district failed every single one of Ohio’s academic school standards.

Justice O'Connor, whose vote is considered crucial in this case, asked both sides whether the impact of quasi-public schools such as charter schools should be considered.

"Why should we not look at all the options open to the parents in having their children educated?" she asked.

Because of the way a lower federal appeals court ruled in finding the program unconstitutional, the Supreme Court is mainly dealing with parents' limited choices within the voucher program itself. Charter schools and their ilk are not part of the program.

But lawyers arguing against the program said that, while it looks like an attempt to give parents more choice about schools, it is in effect granting some families a privilege others don’t get.

"We're asking you to look at the reality," attorney Robert Chanin said. "We're asking you to look at a special benefit that the state of Ohio is making available to a select group of parents."

Justice David H. Souter seemed to be worried more about the privilege churches would get.

"The bottom line is that 96 percent of the kids taking the tuition aid are attending religious schools," he said. "The money's going to end up where it's going to end up, and the 96 percent is pretty persuasive."

The voucher concept — known to its supporters as school choice — faces opposition from the education establishment, which calls it a bad idea that robs public schools of precious dollars and motivated students, as well as from those who believe it violates the constitutional principle of separation of church and state.

Backers say vouchers offer an alternative to wretched public schools where students face long odds against getting a decent education. Students could choose either secular, private academies or parochial schools.

The Constitution does not actually mandate a wall between religion and government, but it does say the government cannot "establish" religion. In practice, that has come to mean the government cannot promote religion or pursue policies that favor one religion over another.

Ohio, backed by the Bush administration, contends that the Cleveland program passes that constitutional test. Parents, not bureaucrats, choose how to spend the voucher money, Solicitor General Theodore Olson wrote in court filings.

The program encourages suburban public schools to take inner-city children, and the fact that no suburban schools have signed up is not the fault of the program, Ohio maintains.

Supporters hope the court will see the case as consistent with its trend toward greater inclusion of religious programs in public facilities, as well as public spending on religious schools.

In the current school year, the Cleveland program is underwriting tuition for 4,456 students, all but a handful of whom are attending some kind of religious school. About three-quarters of the students are attending Catholic schools.

President Bush has supported a national voucher plan since early in his campaign for the White House. Congress rejected private-school vouchers last year, but Bush resurrected the concept in his 2003 budget.

The cases are Zelman v. Simmons-Harris, 00-1751; Hannah Perkins School v. Simmons-Harris, 00-1777; Taylor v. Simmons-Harris, 00-1779.

The Associated Press contributed to this report.