Fairfax County School Superintendent William J. Burkholder, who had been expected to retire at the end of the current school year, announced last night he will stay on to complete "unfinished business."

The 55-year-old Burkholder, who has served in the county's school system for 28 years, the last two as superintendent, had been under what some school officials described as "intense pressure" from the School Board to stay on.

He considered retiring a year ago, but was persuaded to stay on until his contract expires next July. Earlier this year, a committee of three School Board members was chosen to recommend how to choose his successor.

In his announcement to the board last night, Burkholder said, "There will always be some unfinished business, I suppose, at the end of any term. But it seems to me I have quite a bit of unfinished business."

He added that "more and more, I felt a loss not to see the projects through."

Adding specifics, he said: "I want to see significant progress in one area where I see an embarrassment -- minority achievement."

Board members said Burkholder has taken a keen personal interest in improving the achievement of minority students. A study this year showed that black and Hispanic students were consistently falling behind their white and Asian classmates in Fairfax on all indicators of achievement, including standardized test scores and enrollment in advanced courses.

The superintendent said he also wants to ensure the successful launching of a new so-called magnet school in Annandale where science and technology will be stressed and the fostering of ties between the business community and the school system.

"I think the School Board feels this is a time they need a person with experience in Fairfax and a historical knowledge of the problems," Burkholder said after the meeting.

School Board Chairman Mary E. Collier said the board was "extremely pleased and proud to announce that we have persuaded Jack Burkholder to defer his planned retirement."

School officials dismissed the idea that Burkholder, who has a reputation for being a deft and careful politician, was asked to remain in the job so he would not be operating as a "lame duck" while trying to promote a $74.8 million school bond referendum that will go before the voters this fall.

In other business, school officials defended their efforts to correct asbestos contamination in the schools, saying their "program and actions provide a high assurance that students and employes are functioning in a safe school environment."

The school system is reinspecting all its buildings for crumbling asbestos, which can generate minute cancer-causing airborne particles, after the Environmental Protection Agency told officials the earlier inspections did not meet federal requirements.

EPA currently requires that three samples of material suspected to contain asbestos be taken. The school system, complying with an earlier EPA rule, had taken only one sample at each of the locations where asbestos was suspected.

Alton Hlavin, superintendent for facilities services, said the sampling is proceeding swiftly and that the school system is now in compliance with federal record-keeping and notification requirements concerning asbestos.