THE EMPLOYMENT contract of Prince George's County School Superintendent John A. Murphy will not expire until June 1992. Under normal circumstances, that would be reassuring for the county at a time when there is an unusual amount of unrest involving school superintendents elsewhere in this region and in the nation. But the situation in Prince George's has been anything but normal for nearly a year. That's how long it has been since there was any certainty over whether Mr. Murphy would remain on the job.

It began when Mr. Murphy's name appeared as a strong candidate for a superintendent post in Florida last year. Prince George's officials scrambled to offer him an overly long and expensive new contract, and greatly irked black leaders by failing to involve them in the process. Mr. Murphy was stung by the level of protest that ensued. Over the next several months, he said he would leave, and then said he wished to stay. Recently, Mr. Murphy again indicated an interest in seeking other employment.

Although Mr. Murphy has done much to raise the achievement level of the county's schools, officials and the school board were also stung by the criticism of that original contract extension offer and have largely avoided the issue since then.

The school board can and should launch a new debate right now, with participation by the public, on whether to pledge renewal of Mr. Murphy's contract when it expires. Mr. Murphy could then decide whether that is a sufficient vote of confidence. If such an effort failed, Prince George's officials would at least be in a position in which they would have plenty of time to select a new chief administrator.

This would be a timely move for several reasons. Some 16 cities around the nation and three school districts in the region -- Baltimore, the District of Columbia and Montgomery County -- are actively looking for new superintendents.

The Prince George's school board has already made Mr. Murphy the region's highest paid superintendent, but questions remain. Is there sufficient interest on the board and in the county to offer Mr. Murphy assurances on a contract extension? If so, will Mr. Murphy accept? Parents throughout the county deserve answers to those questions. It's time to resolve this situation.