I suppose the leaders of D.C. Public Schools want me to be happy that social studies teacher Kerry Sylvia won’t be coming back to Cardozo Senior High next year. The sound bite sounded appealing when DCPS Chancellor Kaya Henderson announced recently in her new strategic plan that one way to improve graduation rates is to focus on teacher talent — to remove bad teachers and replace them with better ones. But what if, however well intentioned, the reforms are actually leaving uninspired teachers in place and getting rid of some of the best talent?

When I heard that Sylvia had received a notice last month that she was being “excessed” from Cardozo after 13 years, it didn’t add up. I know good teaching, having taught high school for 16 years myself and helped to design the celebrated teacher evaluation system in Montgomery County. My daughter is about to graduate from DCPS, and I have been an engaged parent and a close DCPS observer for 14 years.

Sylvia is clearly a brilliant teacher, committed to her students, her school and its community. She is not only an award-winning teacher but also a leader and student advocate. I’ve talked with her students, several of whom told me that Sylvia’s class was the reason they come to school. If the District’s new plan is eliminating teachers like Sylvia, it’s on the wrong track.

DCPS has one of the highest teacher turnover rates in the nation. Richard Ingersoll of the University of Pennsylvania estimates that, “nationally, on average, about 20 percent of new public school teachers leave their district to teach in another district or leave teaching altogether within one year, one-third do so within two years, and 55 percent do so within five years.” In DCPS, by contrast, 55 percent of new teachers leave in their first two years, according to an analysis by DCPS budget watchdog Mary Levy. Eighty percent are gone by the end of their sixth year. That means that most of the teachers brought in during the past five years are no longer there. By comparison, in Montgomery County just 11.5 percent leave by the end of their second year, and 30 percent by the end of year five. DCPS has become a teacher turnover factory. It has a hard time keeping teachers who are committed to their school and the community it serves.

According to Tom Carroll, president of the National Commission on Teaching and America’s Future, “Teaching is no different than any other profession — experience matters. Researchers have found that teachers reach peak effectiveness with about seven years of experience. But 80 percent of the teachers hired by D.C. this year will be gone before they get there.” Carroll estimates that “the District is burning about $12 million a year on teacher churn — $12 million that is spent hiring and replacing teachers with no gain in school performance.”

Three aspects of the Michelle Rhee-Kaya Henderson reforms contribute to higher rates of teacher churn: unstable school budgets from year to year; greater freedom for principals under the IMPACT evaluation system to identify teachers for dismissal or transfer; and school closings. But most of the turnover comes from teachers leaving voluntarily, not those excessed like Sylvia.

For years, researchers, such as Jane Hannaway of the Urban Institute, have advised DCPS that turnover can be a good thing because odds are that replacement teachers will be better than the ones who leave. But I’ve begun to wonder if perhaps the wrong teachers, in some cases great ones, are being pushed out.

Now, a significant new study by researchers Susanna Loeb of Stanford University, Matthew Ronfeldt of the University of Michigan and Jim Wyckoff of the University of Virginia upends Hannaway’s assumption. The study, “How Teacher Turnover Hurts Student Achievement,” concludes that, separate from the relative quality of teachers who may be brought in to replace those who leave, teacher turnover itself harms a school. Turnover affects morale and the professional culture at a school. It weakens the knowledge base of the staff about students and the community. It weakens collegiality, professional support and trust that teachers depend on in their efforts to improve achievement.

In March, Post reporter Bill Turque penned an insightful profile of another demonstrably terrific teacher, Sarah Wysocki from MacFarland Middle School, who was fired from DCPS after getting low scores in her IMPACT evaluation. The mechanical process of IMPACT insults good teachers and doesn’t do justice to the complexities of good teaching.

If the reform strategies in place in DCPS were working, then perhaps a resolute and unsympathetic response to so-called “soft issues” of staff morale and workforce culture would be understandable. But gains in student achievement in DCPS have stalled. The dropout crisis continues. It’s not that reform isn’t a good idea, but these modest results call for some humility. They might even call for listening to the wisdom of accomplished teachers we can’t afford to lose.

The writer is a DCPS parent, the former president of the Montgomery County teachers union and an education policy analyst at the Economic Policy Institute. He blogs at realeducationreformdc.blogspot.com