When classes start Sept. 7, students in the Washington public schools may have less homework than usual and fewer opportunities to talk with their teachers after school as teachers "work to the rule" because of a labor dispute, teachers union president William Simons said yesterday.

Simons said contract negotiations between the union and the city School Board have been stalled since last spring. The contract expired July 25.

Three weeks ago, Simon said teachers might strike if the old contract was not extended or no agreement was reached on a new one.

Yesterday, he said the union's executive committee and the union leaders of each school decided to let fall classes start "without such drastic action."

Instead, Simons said, "teacher will go in and work from 8:45 a.m. to 3:15 p.m. as we're supposed to do, and that's it. There will be no work taken home, no parental contacts after 3:15 p.m., no extra duties except wher pay is being given."

When teachers leave school for the day, Simons said, "they will carry no briefcases, no books, no nothing until we go back to the bargaining table and start negotiating again."

School Board President Conrad Smith said the board was willing to resume negotiations but wanted to start by dealing with a procedural issue - how many hours teachers serving on the union negotiating committee can be away from their classrooms without losing pay.

Smith said Simons' threat of a "work to the rule" slowdown was "just whistling in the dark." The union leader said the tactic was copied from that of the air traffic controllers in their labor disputes. "I don't believe our teachers would do that sort of thing," Smith said, "I think teachers are much interested in the children than that."

The school board's contract with the teachers union, which represents about 6,500 elementary and secondary teachers, originally expired Jan. 25. Both sides agreed to extend it for six months.

Before substantive talks began, the school board proposed a "prenegotiation agreement," setting out the ground rules for the talks, including a limit of 480 hours that union negotiators can be away from their classrooms.

The current contract and those that preceded it had no such limit, and Smith said contract talks in the past had "a very disruptive effect educationally."

Simons said fewer than five classroom teachers have been involved in the negotiations and that disruption was slight. He said the union believes the language of the old contract applies to the negotiations for a new one, but he offered to submit the meaning of the contract language to binding arbitration.

Negotiators for the board urged that the whole ussue of release time for teacher negotiators be submitted to aneutral third party for "fact-finding" and a recommendation that wouldn't be binding. Neither side has been willing to accept the other's proposal.

Simons said the union asked in June that the contract be extended for three more months, but the school board refused and stopped the check-off of union dues in midsummer.