Catonsville High School senior Scot Cameron and 11 other students expect to read the Bible together during their lunch hour next Thursday, as they do every week. They are relieved, Cameron said yesterday, because they believe a ruling issued this week by Maryland Attorney General Stephen H. Sachs allows them to continue their informal religious activity.

But some school officials are troubled, saying the ruling on student-initiated religious activities issued Thursday may present administrative problems in what is already a sensitive area.

"There are very fine lines in dealing with what is appropriate conduct by students seeking to express their religious beliefs," said Brian J. Porter, spokesman for the Prince George's County schools. "It's very difficult for the school administrator . . . to see that everybody is protected and yet allowed to express their own individuality within the limitations of the school day."

Sachs' ruling, requested by Baltimore County school officials in response to the Catonsville High Bible group, instructs Maryland's public schools to remain "rigorously separate" from free-time religious activities by students. Schools may only "passively" allow such activities and should not become involved by scheduling classroom space or even letting students post meeting notices on school bulletin boards, according to Sachs.

School officials are used to being careful when it comes to religion. In Prince George's County, for example, administrators refer to Christmas trees as "holiday" trees. Yesterday, officials at Charles Carroll Middle School in New Carrollton went one step further and renamed a Christmas pageant a "holiday" pageant, according to William Burba, a teacher at the school.

Administrators yesterday raised questions about whether Sachs' ruling would conflict with school and county regulations covering activities by student groups.

Sachs told principals to say, "What you do with your free time is for you to decide, not us," if asked for permission to meet for religious reasons. It is that advice that Cameron believes sanctions his club's meetings.

Catonsville Principal Lynn Mayer said he also interprets the opinion to mean the students can continue to meet in a classroom as long as they don't ask his permission. While praising Sachs' decision, he said one of the troubling gray areas is what should be considered "free time" and beyond a school's responsibility. Mayer said he does not consider the lunch hour free time.

"I don't want youngsters roaming the building," he said, but added: "I'm marked as trying to restrict these kids and I'm not."

David H. Britton, assistant principal at Thomas S. Wootton High School in Rockville, raised another potential problem. "People cannot just come and use a classroom after school. They do have to touch base with someone . . . . Maybe the chess club is going to meet in there."

Under Sachs' guidelines, if students can use classrooms or other school space for secular activities without asking permission, the same space must be available for religious activities, as long as no staff or nonstudents are involved.

The prohibition against staff involvement raises another problem for some schools, such as Bowie High, where all student activities must be supervised by an adult sponsor.

Robert J. Moser, Bowie vice principal, said Sachs' ruling is "counter to the philosophy we've always had. Any time we have a group of students that meet we have to have a sponsor."