THE D.C. school system’s central office has seen a fair amount of turmoil in recent years, with controversies and changes in school leadership. So there was some understandable worry that the troubles might be felt in the classroom and students would be negatively affected. One encouraging sign that damage has been avoided is the latest, remarkable results from standardized tests that measure students’ college and career readiness.

Results from Partnership for Assessment of Readiness for College and Career (PARCC) tests in English and math were released Monday, and they showed gains by the system in proficiency across student backgrounds, including race, socioeconomic status, ward and gender. Overall, there was a 4.9 percentage-point jump in English scores and a 1.9 percentage-point increase in math. The gains outpaced those of charter schools, which had a 2.9 percentage-point increase in English and a 0.4 percentage-point increase in math.

To be sure, there are significant problems facing the system. The achievement gap between white students and students of color persists, and less than 40 percent of all students are proficient in math or in English. But this is the fourth year the system posted gains on PARCC; and before the rigorous test was introduced in 2015, there were increasing scores on other standardized tests.

That steady, across-the-board improvement is evidence of progress and a testament to the efficacy of school reform started more than a decade ago by former chancellor Michelle A. Rhee and continued by her successor, Kaya Henderson. Ms. Rhee gave a much-needed jolt to the dysfunctional system with an insistence on accountability, and Ms. Henderson brought creative changes to the classroom that included an alignment of the curriculum to Common Core standards, the introduction of more high school electives, an emphasis on interdisciplinary learning and improvements in teacher development.

That students are doing better is because there is better teaching — and much credit goes to those who do this hard, often thankless, work. So it is critical that as the District tackles the formidable challenges still confronting the system, it does not abandon the principles and policies that have resulted in the steady improvement of its public schools.

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