Kaya Henderson, left, talks about her time as D.C. Public Schools chancellor in Mayor Muriel E. Bowser's office on Wednesday. (Marvin Joseph/The Washington Post)

With D.C. Public Schools Chancellor Kaya Henderson announcing that she plans to step down in the fall, Mayor Muriel E. Bowser (D) has a tough decision to make: Does she select someone who has worked under Henderson to replace her, or does she go outside the city to find the school system’s next leader?

Henderson unexpectedly announced Wednesday that she would leave after more than five years as chancellor and nearly a decade after she became joined the effort to carry out an aggressive set of urban education reforms. Bowser immediately tapped John Davis, the school system’s chief of schools, to serve as interim chancellor beginning Oct. 1 and said a national search for a permanent replacement will begin later this year.

Henderson has been credited with leading a troubled and under-enrolled school district through rapid improvements with test scores improving, graduation rates jumping and with more academic and extra-curricular options available in the city’s schools.

D.C. Public Schools Chancellor Kaya Henderson will step down from her position in September. Mayor Muriel E. Bowser (D) shared the news in a statement Wednesday. (WUSA9)

But critics argue that Henderson’s achievements — and the reforms initiated by her predecessor, Michelle Rhee — have not reached the city’s neediest students. The school system’s national standardized test scores have been among the fastest-improving in the nation, but there are still stark achievement gaps between white and black and wealthy and poor students.

Whom the mayor appoints could signal whether Bowser wants to continue along Henderson’s reform path or try a new approach aimed at lifting the city’s poor and minority students.

“Going with an outsider risks the possibility of changing up the agenda and the direction,” said Michael Casserly, executive director of the Council of the Great City Schools. “It’s not unheard of that you could swap out the people and keep the same agenda, but you’ve got to be very strategic and thoughtful and deliberate about doing that.”

City law requires the mayor to assemble a review panel of teachers, parents and students to help her in selecting the chancellor; the panel will relay recommendations to the mayor for consideration. City law also requires that the mayor give “great weight” to recommendations from the Washington Teachers’ Union.

“We are looking internally and we are looking externally, and I don’t go into the discussion with a bias toward either,” Bowser said in an interview Wednesday, adding that she is confident the job opening will attract the nation’s best education talent.

Council member David Grosso (I-At Large), who chairs the council’s Education Committee, said that Rhee and Henderson led D.C. Public Schools through a time when the school system was not completing its most basic functions and was badly in need of close supervision. Grosso said the next chancellor will inherit a far more stable system and will need to work relentlessly to close the achievement gap.

“We are in a transition, where the schools will function with good oversight and management of the system, and now we’re turning the corner,” Grosso said. “I think closing the achievement gap is the paramount problem we’re facing in our school system.”

H.D. Woodson High teacher Laura Fuchs agrees that the next chancellor will need to be prepared to address the inequalities, but she does not think the solution can come from within the school system.

Henderson, Fuchs said, has implemented ambitious policies — such as extended school days and years — but she said the chancellor rarely solicits community input and is out of touch with how those policies play out in schools. Fuchs, who holds a leadership position in the Washington Teachers’ Union, says she knows many of Henderson’s top deputies and thinks it is time for a change.

“They’ve had nine years, and their policies haven’t worked for nine years,” said Fuchs, referring to the combined tenures of Rhee and Henderson. “This is their system, and it’s still not producing results.”

But picking someone from the inside has its advantages, such as institutional knowledge, stability and familiarity with the District. David A. Catania, a former D.C. Council member who chaired the Education Committee, said it is a mistake to “create a cult of personalities” and assume that everyone within the D.C. school system is like-minded.

“The temptation is to look outside for the messiah with all the answers,” Catania said. “Ideally, the best leadership comes from within an organization and not from outside an organization.”

Henderson’s ardent supporters, who view her as a champion of innovative reforms, said they want to see the mayor pick someone who will build on the chancellor’s vision.

“I think Kaya’s long tenure has been a crucial piece of the puzzle for Washington, D.C., and we should be looking for someone who can run the next leg of the marathon, who has a shot at a similar long commitment to our city and our students,” said Katherine Bradley, the president of the CityBridge Foundation and a vocal Henderson supporter. “Typically, public school leadership and policy directions turn over quickly, and that instability retards progress — everything tends to reset with the political cycle.”

U.S. Education Secretary John B. King Jr. said in a statement that Henderson’s dedication and determination have paid off, with a generation of D.C. students being better off because of her leadership.

“Kaya Henderson embodies what any district should look for in a leader: She’s passionate, caring, smart, creative, and, perhaps most importantly, she is driven by a profound commitment to do right by students,” King said.

Henderson said Wednesday that she did not have a favorite pick to succeed her, but she said she thinks Davis is the right choice for interim chancellor. Henderson said she will stay in the District and plans to remain involved in the schools, doing fundraising and advocacy.

“I have put too much blood, sweat and tears into this baby to put it out on the street corner and walk away,” Henderson said. “They are not going to be able to get rid of me that easy.”

Henderson did not reveal any future plans; she said that although she constantly gets job offers, she will not field any for at least six months. But if presumptive Democratic presidential nominee Hillary Clinton were to land in the White House next year and offer Henderson a job in her administration, Henderson said she would definitely consider it.

Emma Brown contributed to this report.