FOR A HOST OF reasons, school superintendents tend to be nomads, spending maybe two or three years in a district before heading for, or being shown, the door. The impressive exception in this region is Edward L. Kelly, who retires today after guiding Prince William County's rapidly changing school system for 18 years. He was willing to continue as superintendent for two more years, but county school board members told him a leadership change after all this time might inject some fresh thinking into the system. A constant contributor of new ideas over the years, Mr. Kelly already is charting new personal paths; he has drafted outlines for two possible books and is considering working as a part-time consultant to school systems.

When Mr. Kelly came to Prince William after 20 years in other systems, the county was mostly country, yet was on the verge of a boom that hasn't stopped. School enrollment was 38,000 students -- slightly more than half of the current total of 66,000 in what is now the second-largest district in Northern Virginia. As reported by The Post's Ian Shapira, the system now has a predominantly minority student body, including substantial African American and Hispanic components.

Mr. Kelly anticipated much of this change early on, and began actively recruiting minority teachers, pressing for all-day kindergarten for some of the poorest students and working closely with the school board and county supervisors on long-range financing for expansion. He also gave principals more autonomy over their schools, in the ways some money could be spent and staff assigned. "My rationale," he said in a 1988 Post interview, "will be to take advantage of the competence and leadership in the building itself. Building personnel know the kids best, and know their needs."

At 63, Mr. Kelly says he feels fine, despite being under treatment since 2002 for a nonmalignant brain tumor. Last week, he played in a benefit golf tournament, with proceeds that will fund a new scholarship in his name, to go to a graduating senior who wants to become a teacher. For months, he has been enjoying an outpouring of gratitude from well-wishers throughout the region. Deservedly so; we join in saluting Ed Kelly for all he did to improve the education of Prince William's students and we wish him well in his next endeavors. It was, as a parent was heard saying at a recent reception, a "hell of a run."