Donald E. Graham is chairman of Graham Holdings Co. and a former publisher of The Washington Post. He is chairman of the D.C. College Access Program and a member of the boards of the D.C. College Success Foundation and KIPP D.C.

This week the D.C. Council’s education committee plans to conduct a performance review of Chancellor Kaya Henderson. District residents might want to follow Henderson’s appearance before the council.

The evaluation will tell us a great deal — not about Henderson (on her, the results are in) but about the council members performing the evaluation, particularly those who wish to be mayor.

For those who have followed the D.C. Public Schools for a long time, the district’s upward movement in test scores seems almost miraculous. The accompanying chart shows the performance of D.C. fourth-graders on the past four “Nation’s Report Cards,” as the National Assessment of Educational Progress is known. The chart comes from the CityBridge Foundation, which has much more such information on its Web site.

The importance of test scores can certainly be overrated, but for many years D.C. results all sat in one place: the bottom. There was a time when, on these same federal tests, the District had the country’s worst-performing school system. Our schools were struggling, no one seemed to have the answers, and no other city showed a model of sustained improvement.

Now there is such a city and . . . it’s Washington, D.C.! Education Secretary Arne Duncan has called the D.C. results “a pretty remarkable story.” Our students have shown steady, large-scale improvement on not only the federally administered NAEP tests but also on the city’s DC-CAS tests and, to a lesser extent, on the SAT, where progress is crucial. “DCPS’s gains in reading and math were larger than those of any other city, the large-city average, and the national average,” CityBridge’s leader, Katherine Bradley, said of the 2013 NAEP results.

In previous decades, residents who cared about students longed for one thing: a leader who would make the schools gradually better and start the necessarily years-long process of making D.C. public education truly outstanding.

That leader is here. Such substantial improvement has been demonstrated that one can only wonder what is possible in the next few years, assuming that the same leadership is kept in place. In fact, when one considers that the District has truly remarkable charter-school educators producing impressive results alongside the public schools, the outlook for education in the District has never been better.

What could possibly go wrong?

Longtime D.C. residents know the answer: D.C. politicians. The sight of a successful school superintendent seems to infuriate the city’s elected political leaders. In the old days, the elected school board could be counted on to make a successful school leader’s life miserable until he or she left. Now the D.C. Council, which to its great credit voted for mayoral control of the schools in 2007, has lurched back into the breach and wishes to provide “oversight” (that is, distraction and bad advice) to an able chancellor.

To do this, one has to ignore the obvious (D.C. schools are improving as fast as any in the country) and focus on the equally obvious (there is still a need for substantial improvement — and no one is saying so more loudly than Henderson).

Test data show that most D.C. fourth-graders are still performing below grade level — something that must and can change. But look also at the 2007 scores. Would you have believed then that D.C. schools could improve in six years’ time as they have? They had not done so before. What other city has done as well?

While the District has struggled over the past 40 years, it has been surrounded by many high-performing suburban school systems. Most of these have enjoyed excellent leaders for long periods. Mike Hickey was the Howard County superintendent for 16 years; Jerry Weast led Montgomery schools for 12; Ed Hatrick just announced his retirement after a 22-year run in Loudoun County; the late Ed Kelly led Prince William for 18. Meanwhile, the District has had seven superintendents in the past 18 years, not counting a couple of long-service interims. No, having just any superintendent for 15 years won’t solve the city’s problems. But rotating them every two or three years ensures that the problems never get solved.

If you wonder why D.C. Council members might be slow to support Henderson, here are a few good guesses:

1. The D.C. teachers union, like those in big cities everywhere, longs to reclaim the control it used to have over the school system. Its campaign contributions and volunteer workers go to those who oppose Henderson (although under her, relations with the union are much improved). Watch and see if your council member is more influenced by improving schools or by union campaign support.

2. Several D.C. Council members, like a branch of the Flat Earth Society, insist in the face of mountains of evidence that no progress is being made in the city’s public schools and that the amazing results in the high-performing charters aren’t really happening. As to why politicians believe this, see (1) above.

3. The school system provides a rich trove of patronage and power when it isn’t run by a strong leader. Former mayors and school board members planted their allies in its jobs. Kaya Henderson will not stand for that. The council’s education committee chairman, David Catania, a bully for whom no strong leader would ever work, is not a patronage junkie but is the council’s leading would-be micromanager.

For the majority of DCPS students — those who come from very low-income families — the stakes couldn’t be higher. For 15 years I have been chairman of the D.C. College Access Program. We have worked to increase the number of D.C. public school graduates going to college and heard them explain what’s at stake — college is their one chance to escape the tough circumstances they were born into. They want a different and better life, and education is their best opportunity.

For 15 years D.C. residents have prayed for improved academic results from our high school students. If those results come, scholarship money will rain down. We aren’t there yet. But we have the greatest opportunity ever for a much-improved DCPS. All we have to do is keep Kaya Henderson and her team on the job. D.C. voters: Tell your council members to get out of the way and let the D.C. educator continue to do her job.

And don’t dream of voting for a mayoral candidate who doesn’t support her.