WHEN JOSEPHINE BAKER was approached about joining the District’s new public charter school board, the first thing she had to do was find out what these newfangled schools were all about. It was 1996 and the national charter school movement was in its infancy. What won her over was the belief that D.C. children deserved better education choices than the dismal ones the city’s system offered. That the District today is a model for education choice is evidence of her leadership and why replacing her will be a challenge.

Ms. Baker announced Wednesday that she will step down as executive director of the D.C. Public Charter School Board at the end of this month. Appointed to the board after Congress passed legislation to foster charter-school growth, Ms. Baker was elected as the board’s first chairman and in 2002 became executive director. During her tenure the city’s charter system grew from a handful of schools to the current 52 charters on 93 campuses.

So popular are charter schools — nearly 40 percent of D.C. public school students attend them — that it’s hard to recall their rocky start or how city and school officials vilified them as a Republican Congress’s intrusion into local affairs. “Didn’t care, didn’t matter,” Ms. Baker told us of not knowing the political persuasion of charter backers and instead focusing on the “best interests of the children.” Charters have provided a healthy alternative to parents eager to escape bad schools, thus helping spark the education reform that has brought marked improvement in the traditional schools. Consider, for example, that when charter schools were introduced, about half of the city’s high school students dropped out before graduation; the 2010 high school graduation rate for charters was 83.5 percent and 72.3 percent for the public school system.

A hallmark of the public charter school board has been its willingness to close schools that weren’t producing results. Twenty-eight charters have closed since the movement began, not including two going through the revocation process, and all those closed by the board were in the bottom quartile academically.

Among the remaining challenges is getting a fair share of public resources and support from an establishment that still has the tendency to see charters as undermining traditional schools. In fact, competition from charters helped drive reform of the public school system, and the two systems (along with private-school vouchers) give parents critical choice in their children’s futures. As Ms. Baker pointed out, what is most important about a school is not whether it is charter or non-charter, but whether it is any good.