RELEASING preliminary results of the latest student achievement tests, D.C. officials focused on the positive. Middle school students in the traditional public school system have made dramatic progress. Students in every grade of public charter schools tested made gains this year in both reading and math. Both traditional and charter schools have shown steady improvement in student achievement over the past five years. Clearly, there is much to celebrate.

But the test results also show how much remains to be accomplished. With the lone exception of high school math, a majority of children in the District’s public charters and traditional school system are not proficient in reading or math. It is simply scandalous that in the nation’s capital, only 43.9 percent of elementary students can read on grade level, that only 43.3 percent of them are proficient in elementary math or that, in the one area where a majority of students are proficient, sizable numbers (47.2 percent) are still failing.

Mourning those numbers does not detract from the achievements of education reform that began in 2007, when the public school system was placed under the control of then-Mayor Adrian M. Fenty. The gains in test scores over five years — from an increase of 5.54 percentage points in elementary reading to a 19.35-point boost in secondary math — testify to the work begun by former schools chancellor Michelle A. Rhee in setting higher expectations and making the system accountable for results. But the leveling of scores in recent years — elementary scores in both reading and math even dipped slightly this year — suggests that even harder work lies ahead. It’s clear that some of the early gains were attributed to what officials called picking the low-hanging fruit: ensuring instructional materials were in place or doing better at test preparation. Apparent anomalies on some test sheets in 2009 prompted some to question whether cheating occurred; outside consultants found possible testing improprieties in three of 14 classrooms flagged for investigation but found no conclusive evidence of cheating; further investigation is underway.

National tests administered independently buttress signs of progress in the D.C. schools, showing significant gains in reading and math between 2007 and 2009.

As she looks ahead, Schools Chancellor Kaya Henderson talks about the need for continued “radical changes.” Included is a transition to more rigorous “common core” standards, introduction of a rich curriculum and more high-quality professional development for teachers. There must be no retreat from the insistence on good teaching that is enshrined in the system’s IMPACT evaluations of its professionals. An omen of continued school improvement is the commitment shown by Mayor Vincent C. Gray (D), who was able to see past his differences with Ms. Rhee in picking her top deputy to lead the schools. Not only has Mr. Gray given Ms. Henderson the fiscal resources, but also, to date, he’s given her the room and backing to make her own decisions. And, in welcome contrast to his predecessor, Mr. Gray has fully embraced the public charter schools, which serve 40 percent of D.C. students, as a crucial part of school reform, creating healthy competition and generating progress.

In the coming weeks, test results will be finalized and data will be more deeply analyzed to help chart future changes. The system’s hardworking teachers and principals should take pride in the progress — and find motivation in the number of children who continue to be left behind.