Alexandria School Superintendent John L. Bristol, the sometimes controversial administrator who presided over attempts to keep the city's schools racially balanced, has resigned to take a better paying position in the Midwest.

Bristol, 47, whose resignation will take effect July 31, will become superintendent of Lyons Township school district in LaGrange, Ill., at an annual salary of $59,000. He is paid $51,300 in his current post.

Bristol revealed his decision in a surprise announcement to School Board members in an executive session Wednesday night.

His departure is the latest in a small exodus of top school officials from the Washington area. The superintendents of Fairfax and Montgomery counties also have resigned within the last year. In addition, the chief school administrators in Arlington and Prince George's counties have recently come under fire in school policy disputes.

"The average life span of a school superintendent's job in the United States today is about three years," said Alexandria School Board Chairman Alison May yesterday. "Many of us very much wanted John to stay, but we understand that he accepted the job for financial reasons."

Bristol, who came to Alexandria three years ago, has $13,000 vested in the Illinois employe retirement system from more than a decade's tenure in Illinois schools, May said. He has four children.

Bristol was in LaGrange, about 13 miles west of Chicago, yesterday and was unavailable for comment.

The system he will head there has three schools and about 4,500 students, compared with the 18 schools and 11,000 students in Alexandria.

At least one Alexandria School Board member suggested yesterday that salary might not be the sole motive for Bristol's move.

"I suspect he was not cut out for the pressures of Alexandria," said William D. Euille, who said he often criticized in private what he saw as Bristol's aloofness and insensitivity to racial matters.

"He was a good manager, but a stern manager," Euille said. "He never understood why blacks objected to two schools in black neighborhoodss being closed at the same time. He can be a personable man, and not a racist, but he could be insensitive at times."

Bristol leaves a school system whose enrollment appears to have stabilized after dropping sharply since racial integration was begun in 1970. At the time, white students outnumbered blacks nearly three to one. After integration, white enrollment plummeted while the number of blacks in the system inched upward.

Today, school officials said blacks and whites are nearly balanced, with 5,470 whites, and 5,028 blacks and 965 students of other races.

The school board uses a complex system of paired residential neighborhoods to achieve racial balance in individual schools. Under Bristol's administration, five schools have been closed because of enrollment increases.

In 1978, a year after Bristol was hired, the Alexandria NAACP chapter filed a lawsuit against the School Board in federal court, claiming that the Robert E. Lee and Cora Kelly elementary schools were closed because the schools are in predominantly black neighborhoods.

Last year a federal judge dismissed the case. It is now on appeal, although the NAACP has dropped out of the matter.

Cora Kelly Elementary is scheduled for reopening.

"I'm really sorry he's leaving," said board member Judy Feaver yesterday. "He came in with a difficult assignment to reorganize the system, deal with declining enrollments and bring the budget under control. If he was unpopular with some people, I think it was because of that."

The overall decline in enrollment has resulted in some city schools being used by only a fraction of the students who once occupied them. At the same time, inflation, and the increasingly specialized -- and expensive -- nature of education pushed the administration budget "through the roof," according to May.

The school system depends entirely for its budget -- now $34 million -- on the Alexandria City Council, which in the mid-1970's began for the first time to criticize school officials for inefficient management practices, she said.

Bristol replaced Superintendent John Albohm, a genial educator who headed the system for 14 years and steered it through the years of integration "almost by the force of his personality," according to one city official. "But there was almost no good management over there," he said.

Bristol brought in more computers, convinced the board to take an unpopular school closings, and took the heat from increasingly militant Alexandria teachers.

His plan to create a second senior high in the city last year, however, was sharply rebuffed by even his allies on the board. Many privately argued that such a scheme would revive the segregated system that had recently been dismantled.

Bristol also never managed to capture the confidence of city officials and council members, many of whom criticized him for imprecise budget plans.

Nonetheless, Vice Mayor Robert L. Calhoun, one of Bristol's sharpest critics last year, said yesterday, "I'm going to miss him. He is a tough, candid, hardworking guy, and faced up to some difficult issues."