Prince William County School Superintendent Edward L. Kelly announced yesterday that he will step down at the end of this school year, his 18th at the helm of the state's third-largest school district.

Kelly, 62, the longest-serving superintendent in the Washington area, asked the School Board this summer to extend his contract two years when it expires in June, despite a brain tumor and other health problems that sidelined him for part of the previous academic year. But he said that in one-on-one conversations with board members, it became clear that most wanted a change in leadership.

He withdrew his request for an extension during a closed School Board meeting Wednesday and told his staff yesterday.

"Heated discussions would not have been in anyone's best interest," Kelly said at a news conference yesterday afternoon.

Acknowledging his disappointment, he cited recent initiatives -- including all-day kindergarten for some of the poorest students -- and newly hired administrators. "I think I had a lot to offer," he said. "I could have been some help to them. I didn't want to start these initiatives and just walk away."

He also spoke fondly of his staff. "I love the people with whom I work. The associate superintendents, the principals, the teachers are as fine a group of people that you could ever ask for."

The School Board plans to meet Sept. 29 to discuss the search for his successor.

Kelly said he learned over the summer that board members wanted two things: change and "their own superintendent." Last year's election brought four new members to the eight-person board.

Kelly said no one criticized him specifically, and members interviewed yesterday mentioned no specific failings or changes.

"I think that's probably because everyone on the board has a different idea of what change means," said Milton C. Johns (Brentsville), a first-term member. "I felt that to move to the next level, it's time for new ideas and new leadership."

Grant Lattin (Occoquan), also a new member and a retired Marine officer, likened it to the military. When commanders are replaced, he said, "it almost never was because the previous commander was doing a bad job. That was just the way the system worked."

Lattin said new commanders often galvanized the people they led. Kelly "served well for 18 years. Now it's time for somebody with . . . a new vision," he said.

School Board Chairman Lucy S. Beauchamp (At Large), the longest-serving member at 13 years, said she did not want to see Kelly leave. "There aren't any superintendents out there as fine as he is," she said.

Kelly has been superintendent since July 1987. Before that, he served as superintendent in Little Rock. He lives in the Manassas area with his wife, Lynn. All four of their children graduated from Prince William schools.

Kelly said he did not believe his health played a role in the board's thinking. He is receiving outpatient treatment at Johns Hopkins Hospital for the brain tumor and suffered a serious infection after a hernia operation last year. He said he has recovered from the infection, adding, "I'm as strong as I've ever been."

Alison Nourse-Miller, an associate superintendent overseeing 20 county schools, said many staff members were surprised and saddened to learn that Kelly was planning to step down. A Prince William school employee since 1978, Nourse-Miller praised Kelly for improving the county's reputation among state school districts.

"One of his legacies is he truly does believe all children can learn," she said.

Kelly echoed that comment when asked about his accomplishments, citing an improved focus on instruction as chief among them. "That's the basis for all the other initiatives," he said.

Kelly said he will have as much impact as he can in his final year. "I'm not shy about bringing new ideas forward," he said.

Edward L. Kelly announces his departure at the end of the school year. With him at the news conference is School Board Chairman Lucy S. Beauchamp.Kelly hoped to stay two more years to see through his initiatives -- "I think I had a lot to offer" -- but said board members wanted a change in direction.