The Supreme Court heard arguments this week in a case that questioned whether federal enforcement of collective bargaining 'aws in Catholic schools violates constitutional guarantees of religious freed in.

While the immediate case involves two Catholic heigh schools in Chicago and five in northern Indiana, the issue is one that affects more than 100,000 lay teachers in some 10,000 secondary and elementary Catholic schools across the country.

The court's decision, which will be handed down sometime before the current term ends, could also conceivabily set precedents in the righly sensitive area of state aid to parochial schools.

The current case began more than two years ago when lay teachers at the two schools appealed to the National Labor Relations Board to force Catholic bishop - under church law the heads of the schools - to bargain collectively with them.

When the Court of Appeals for the 7th Circuit upheld the bishops' contention that such an order involved excessive entanglement by the government in affairs of religion, the NLRB took the issue to the Supreme Court.

In arguing for the bishops, Chicago attorney Don H. Reuben referred repeatedly to past court decisions that over the years have struck down various forms of state aid to parochial schools.

"We are in a no-win situation." Reuben complained. Catholic schools have been described by this court numerous times" in parochial aid cases as existing primarily "to perpetuate the faith . . . to bring young men to the priesthood," he told the justices.

"Now to have the same schools be treated as secular, eligible for regulation . . . offends my sense of fairness," he said.

Reuben complained that in all the parochial aid cases the court has found that lay teacher has been subject to the authority, the command of the bishop."

Given this understanding of Catholic schools, he continued, "on its face, NLRB incursion into religious schools is an abrogation of the First Amendment."

Arguing for the government. Solicitor General Wade H. McCree Jr. denied that the schools were religious. "They are secular in all respects" and comparable to public schools, save for the addition of required courses in religion, he said.

The schools "send the majority of their students to secualr colleges," he said, adding that the Indiana schools admit "some non-Catholic students."

Under questioning by the court.McCrea pointed out that religious convictions about collective bargaining were not at issue here. On the contrary, he emphasized, the Catholic Church, nationally and internationally, has been highly supportive of the rights of labor to organize aid bargain collectively.

"The threshold question is whether the conduct complained of (the NLRB order to bargain collectively with the lay teachers) is in the area mandated by religious belief," he said.

"We believe that in this case the order to bargain with the elected representative doesn't involve" an infringement of the free exercise of religion, as guaranteed by the Constitution, he said.