D.C. Public Schools Chancellor Kaya Henderson, shown in 2015, announced Wednesday that she will step down in September. (Jabin Botsford/The Washington Post)

“LEADERSHIP IS about knowing when to pass the baton.” That was the comment from D.C. Public Schools Chancellor Kaya Henderson in announcing she will leave office in the fall. Because her leadership of the public school system, first as deputy and then as its head, has been peerless, we will bow to her judgment that this is the right time for her to go. That, though, doesn’t mean she won’t be sorely missed. Her departure is a loss for the District and its public school students, and it is critical that a successor be found who is committed to furthering the improvements in D.C. public education.

Ms. Henderson’s departure, announced Wednesday, is unexpected, but both she and Mayor Muriel E. Bowser (D) said it was voluntary, the result of Ms. Henderson being tired from her long tenure and in need of a change. Her last day on the job will be Sept. 30, and John Davis, the school system’s chief of schools, will serve as interim chancellor while a national search for a permanent replacement is conducted. Ms. Henderson said that September, once schools are up and running, is the least disruptive time for change.

This fall will be the six-year anniversary of Ms. Henderson taking over leadership of the schools from then-Chancellor Michelle A. Rhee, under whom Ms. Henderson was deputy during the turbulent early years of school reform that followed the introduction of mayoral control. When Ms. Rhee and Ms. Henderson arrived in 2007, the system was broken. Schools could not open on time, classrooms lacked textbooks, enrollment was on the decline and, instead of expectations about children learning, there were excuses for why they were not.

Today, the system is the fastest-improving urban school district in the country, with better student test scores, increased rigor in the academic curriculum, new extracurricular offerings and rising student enrollment . That there was a continuity of leadership and agreement on what needed to be done — even when mayors and chancellors changed — was clearly a factor in the system’s progress. To be sure, the system is still a long way from being where it needs to be. The vast majority of students are still not proficient in reading and math, and an achievement gap between minority students and their white peers persists.

Because there is still much work to be done in fixing schools, Ms. Bowser must give great care to picking a replacement; it could prove to be her most important appointment. The mayor’s choice must be confirmed by the D.C. Council, which we hope will forgo politics and focus instead on what — and who — will best serve the city’s students.