Most Boston University (B.U.) students returned to classes yesterday after a nine-day faculty strike, but many professors moved their classes outdoors or off campus to avoid crossing picket lines of still-striking clerical workers and librarians.

The faculty union officially ended its strike Friday night when its members ratified a three-year contract. However, many faculty members said they would honor the picket lines of the 800 clerical workers and 20 librarians, who are still on strike demanding that the university recognize their unions and meet with them for contract negotiations.

Yesterday was the first day of classes since the faculty strike ended, because B.U. remained closed Monday in observance of Patriots' Day.

"We're back to semi-normal," J. Kenneth Menges, president of the student union, said yesterday. "The situation will take a long time to heal, but at least we're on the right track," he added.

Menges estimated that 75 per cent of classes were held, many of them outside. People around the university said that classes were generally well-attended.

Linda Hansen, a teaching fellow in history, said yesterday she held her class in the office of the B.U. Exposure newspaper to show support for the clerical workers and librarians.

"I would not feel right crossing the picket lines, but I do feel an obligation to my students," she said. "If we hadn't resumed classes, this semester would have been a bust," she added.

Arranging a Date

A spokesman for the faculty union said yesterday faculty members expect to be paid for all classes they teach, including classes held off-campus.

Federal mediator Gerard M. Gomez, who arranged the all-night negotiation sessions which resulted last week in the faculty contract, said yesterday that at the request of the clerical workers he had tried to arrange a meeting for them with the university trustees, but the trustees rejected such a meeting.

University spokesmen yesterday declined to comment.

The clerical workers yesterday demanded at a membership meeting that the university recognize their union, begin contract negotiations with union representatives and then submit disputed points to binding arbitration.

University trustees were unavailable for comment yesterday, but trustee Robert C. Bergenheim said last week the university probably will not submit labor disputes to binding arbitration.

The National Labor Relations Board has certified the unions for the clerical workers and librarians; but the university has appealed that decision, and the issue is expected to remain in the courts for at least two years.