I first became aware of efforts to close achievement gaps in Lexington, Massachusetts, in 2008, when I met the relatively new superintendent, Paul Ash, at an achievement gap conference organized at Harvard by Ronald Ferguson. Ash struck me as a serious educator who was concerned that African American students were not doing as well as white students and determined to do something about it.

And apparently he has.

A recent report, which I talk about this week in Huffington Post, documents that Lexington has significantly narrowed achievement gaps and draws on interviews and surveys to report on many of the things that Ash set in motion as superintendent.

As with any story of improvement, Lexington’s is not a simple one to tell. As Ann Ballantine, one of the authors of the aforementioned report, told me, Ash was “propelled by a belief that collaborative teaching results in higher-quality teaching. By sharing and supporting each other through the use of professional learning communities and extensive professional learning, all teachers become better teachers — which means anyone can improve. Even if you’re outstanding, you can get better.”

But establishing the kind of collaborative structures in which teachers could share expertise and solve the deep questions of why some children weren’t learning to read, write, or do math at high levels took a lot of work.

One of the very first steps Ash took was to hire the retiring president of the union, Vito LaMura, to write a report on the achievement gap — which, the report quotes a teacher as saying, “crystallized tangible information, data on test scores and such, in an honest and real way that made it easier for educators to wrap their heads around it.”

That led to a committee, which led to a lot of initiatives and programs — professional learning communities, response to intervention, and after-school tutoring, to name just a few. All were focused on raising the achievement first of students in METCO, a voluntary desegregation program, but then on all the district’s struggling students, no matter where they were from.

The initiatives became a little overwhelming to many teachers. “The backlash came when people felt overwhelmed — they didn’t see the coherence,” Ash told me recently. But, he added, once collaborating on what kids need to learn, how to teach it, and what to do when kids don’t learn it the first time “becomes the way we run things, it is no longer a problem and [all the practices become] self-sustaining.”

However, he said, “without a superintendent committed to the cause who will stick around a while, it won’t happen.”

When he thinks about the work he did as superintendent — he is in the process of retiring now — he thinks about individual students, including one young African American woman who traveled on the bus from Boston for her whole school life. In high school, she got the highest score possible on five Advanced Placement exams. She hadn’t been a particularly high-performing student earlier in her career, but as she got additional help and succeeded she developed more confidence and better work habits. She now has many more opportunities available to her than she might have had if the initiatives Lexington put in place not been there.

“You can change their whole life,” Ash said.