Maryland Attorney General Stephen H. Sachs issued strict guidelines today limiting student-initiated religious activity in the state's 300 public high schools and challenged the constitutionality of a national religious "equal access" law enacted last summer by Congress.

In a 31-page opinion that school administrators say will fuel the nationwide debate over the separation of church and state, Sachs said public schools may only "passively" allow prayer sessions and other activities and in no way facilitate them, not even to the extent of allowing students to post notices of religious meetings on school bulletin boards.

"What is essential," Sachs said, " . . . is that the school remain rigorously separate, even distant, from these free-time religious activities. It may not allow itself to become involved in any way in the students' religious activities, whether by scheduling them, by granting permission for the use of space . . . or by monitoring religious gatherings in any but the most general way necessary to assure against misconduct."

Sachs' opinion arises from a brief squabble last spring at Catonsville High School in suburban Baltimore County, where some students were denied permission to hold Bible study sessions in a vacant classroom during their lunch break. School principal Frank L. Mayer agreed to let them to use the school cafeteria. The students complained that it was too noisy. The county superintendent's office overruled Mayer, and the students were allowed to use the classroom. At the same time, the superintendent's office asked Sachs for a clarification on the issue.

At one point in the opinion questioned sharply by several school administrators today, Sachs said school authorities may neither grant nor refuse permission for religious activity and must take a position only of "passive toleration" in order to meet the constitutional requirement of government neutrality.

"What you do with your free time is for you to decide, not us," Sachs suggested school principals should tell students requesting permission for religious activity. Sachs said a school could set aside a vacant classroom as long as it was available to both secular and religious activities, but it could not schedule religious activities in the room.

"That's one area where there may be problems," said Mayer of Catonsville High. " . . . If I say go ahead and do what you want, that's not a way to run a school . . . . Scheduling of room space could become a problem."

Nonetheless, said Mayer, "it was a difficult decision for Mr. Sachs. Here's a man running for governor and he's not going to please everyone."

One local school system that may have a problem with Sachs' ruling -- although for an unusual reason -- is Prince George's County where, according to spokesman Brian Porter, school policy flatly prohibits any free-time group religious activity. "It appears our policy is not consistent with the Sachs opinion , but we need to review it first," Porter said.

In the opinion, Sachs said, "The issue of student-initiated religious meetings in the public schools stands at the confluence of the First Amendment principles that are of vital importance and yet in fundamental tension with one another . . . it often seems necessary to say two contradictory things at once. But the . . . price of religious liberty is official neutrality."

Sachs also said the so-called "equal access" law passed by Congress last summer oversteps what should be a school's neutrality by requiring it to grant religious groups the same access to school facilities as secular groups. He said the law is "simplistic . . . and constitutionally intolerable."