The Prince George's County Board of Education has rejected a proposal made by negotiators for county teachers that sought a board guarantee that teachers could go to binding arbitration with their grievances in the 1984-85 school year.

Instead, the board would agree only to negotiate that point as part of next year's contract talks, according to Brian J. Porter, school system spokesman.

The teachers, who have been without a contract since August, told the board on Thursday that they would be willing to settle the present dispute if the board would agree to grant the teachers the right to binding arbitration over grievances as part of next year's contract. In earlier contract talks, the teachers had attempted to get the board to agree to binding arbitration of grievances as part of this year's contract.

The issue of binding arbitration is the last remaining point of contention between the teachers and the school board.

"We were willing to put the thing off for a year. We thought we had made a big concession . . . . The board is being really obstinate about this," said Paul Pinsky, president of the Prince George's County Educators Association, the bargaining agent for the teachers.

Porter said the board action "represents a good faith gesture . . . to recognize the need to discuss and negotiate" the issue. He said the board is willing to discuss the issue of binding arbitration only "in the context of a full range of contractual issues . . . . They do not want the issue of binding arbitration to stand alone."

Pinsky said the association's executive council would discuss the board's latest action at a meeting on Wednesday, after which the association will decide on its next course of action.

In a related development, the Prince George's County Council of Parent Teacher Associations, which represents about 190 local PTAs passed a resolution this week urging the school board to agree to the teachers' contract demands.