The Prince George's County school board remained firm last night in its rejection of teacher-contract terms put forward by an independent labor mediator despite urging by County Executive Parris Glendening for a settlement.

Earlier in the day, Glendening held a press conference to encourage the board to end its contract stalemate with the teachers union. He said a continuing stalemate would be "unproductive and cause an air of confrontation" when school opens next week. The union--the Prince George's County Educators Association--has already endorsed the labor mediator's proposals, including one for binding arbitration for dealing with teacher grievances.

Following Glendening's press conference, the union's 200-member representative council unanimously approved plans for a media campaign and a mass rally to pressure school board members at the board's regular meeting on Sept. 1--the day the present teacher contract expires. Union officials said they were not prepared to call for any job action over the contract.

Last night the school board held a special closed session to reconsider its earlier, near-unanimous position against binding arbitration, which the mediator proposed as a tradeoff for the teachers not getting a cost-of-living raise this year.

Schools spokesman Brian J. Porter said after the session that the board "does not believe that binding arbitration is necessary or desirable at this time" and that it "would jeopardize the management of the school system."

Union President Paul Pinsky, reached for comment on the board's decision, said, "We were hoping they'd be reasonable, but it looks like they want a confrontation. It's just that simple. We haven't even talked formally about a strike yet, but it's becoming a hot topic."

He said that based on the response of the teacher representatives yesterday afternoon, he would not sign a contract without binding arbitration. He said 16 of Maryland's 24 jurisdictions have teacher contracts providing for binding arbitration.

Some board members have said that Glendening's entry into the contract dispute last week contributed to the board's rejection on Thursday of a compromise settlement that included the mediator's recommendations.

At his press conference, Glendening said he supported the tradeoff of binding arbitration of grievances in exchange for giving up cost-of-living raises and praised the teachers' willingness to join other county labor groups in forgoing such raises.

"Both sides benefited a little bit," he said. "That's what fair negotiations are all about."

Before last Thursday's contract vote by the board the executive, at the urging of Pinsky, had telephoned several board members and urged them to accept the compromise.

Pinsky said that when he asked Assistant Superintendent Edward Felegy, who helped draw up the rejected settlement, what went wrong, Felegy told him, "You should never have gotten Glendening involved."

Board members said last week that Glendening's intervention was resented and contributed partially to their rejection of binding arbitration.

Glendening, in defending his actions yesterday, pointed out that the school board entreated him for special support in the tight county budget last spring.

"Certainly they asked me to help on funding," Glendening said. "I thought that mutually offered assistance in reaching a solution is appropriate," he added.

The school board has approved contract provisions that would reduce the teacher work year from 189 to 187 days and give a $186 payment to about 2,200 teachers who would otherwise not receive normal longevity increases under the existing contract. The $186 would cover increased costs of medical and other benefits this year.

But the board remains adamant in opposing binding arbitration , seeing it as jeopardizing its right as a body of elected officials to manage the school system by surrendering power to a third-party labor arbitrator.