Richard W. Johnson, who was fired Jan. 1 as Prince William County school superintendent after nearly a year of bitter debate over his leadership, will become Loudoun County's assistant superintendent for support services beginning July 1.

Johnson, 46, was the Loudoun County School Board's unanimous choice this week for the position, which involves purchasing and contract management as well as overseeing maintenance of the county's 32 schools, athletic fields and school bus system.

Loudoun, like neighboring Prince William, is facing an expanding enrollment spurred by an influx of new residents. The county has 13,000 students and 900 teachers.

Johnson accepted a one-year contract paying $59,000, according to Superintendent Robert E. Butt. Prince William officials bought out the more than two years that remained on Johnson's contract there, at $71,200 a year.

Johnson was ousted in Prince William, where he had been superintendent since 1980, after debate mounted over what critics called his abrasive style and poor relations with some board members, county supervisors, teachers and parents.

Supporters credited Johnson with aggressive management that saved Prince William's schools from being overwhelmed by growth. During his tenure, the county built five schools and doubled its education budget to $161 million.

Asked about Johnson's track record, Loudoun School Board Chairman Betty S. Poehlman said yesterday that his new job "is not a position that deals with hiring and personnel issues, nor does it deal with instruction."

Butt echoed her remarks. Noting that some people had questioned Johnson's record with teachers and other groups, Butt said, "Those questions have nothing to do with this job because he won't be working with teachers." He said Johnson was hired for his expertise in dealing with an expanding school system.

During the next five years, millions of dollars will be spent on five new schools in Loudoun County, including three elementary schools, Butt said. "I wanted the best-qualified person to spend all that money and to spend it in the most efficient manner, and that's where his record stands out," Butt said of Johnson, who was regarded as a master of detail in Prince William.