The District public school system's chief of staff, who has overseen day-to-day operations for a year and a half, yesterday announced his resignation effective Jan. 25, saying he planned to start an educational consulting firm.

Steven G. Seleznow has served as the top deputy to Superintendent Paul L. Vance since March 2001 and filled in for Vance for more than two months when the superintendent was recovering from double-bypass heart surgery.

Seleznow said that he came to the school system to help improve key operations and that many of his goals had been achieved. "At this stage in my life, I want to pursue some other professional opportunities," he said.

Vance said that when he hired Seleznow, they had an understanding he would stay for only a year -- an arrangement that was not made public at the time.

Vance credited Seleznow with overseeing a number of initiatives, such as crafting a business plan to improve basic functions of the 67,500-student system, overhauling low-performing schools and developing a budget with specific goals and performance measures.

"There were certain things I needed done, and I needed them done quickly and in a certain way," Vance said yesterday. "I knew Steve could do that."

Seleznow worked for Vance for years in Montgomery County, where Vance was superintendent. Vance said that he had known for several months about Seleznow's plans to leave and that he has prepared a list of possible successors.

D.C. Council member Kevin P. Chavous (D-Ward 7), who chairs the council's education committee, expressed concern that Seleznow's departure could create instability.

"It is a loss inasmuch as it has become increasingly clear that Dr. Vance was relying on Seleznow for a number of things," Chavous said.

Seleznow said he was leaving with the school system on stronger footing.

He will become president and chief executive of Humanitas Consulting, a start-up firm that will work with organizations that serve children. Seleznow said he will consult on personnel and leadership development and strategic planning.

Vance said Seleznow, whose salary is $145,000 a year, will be paid on a per diem basis to raise money for the school system from private sources and develop private partnerships.

Chief of Staff Steven G. Seleznow says that the D.C. school system is in better shape now and that he has accomplished much of what he sought to do.