Correction: Cornerstone assignments are required by D.C.Public Schools. An earlier version of this commentary incorrectly said that cornerstone assignments are not required. This version has been updated.

D.C. Schools Chancellor Kaya Henderson. (Sarah L. Voisin/The Washington Post)

For several years, D.C. Public Schools has been at the forefront of a movement to give students a coherent body of knowledge starting in kindergarten. It’s a commendable effort but still a work in progress.

Some of DCPS’s education reform efforts, such as teacher evaluations and school closures, have drawn a lot of attention. But few people have noticed a fundamental initiative to change what and how teachers teach. If successful, it could help narrow the District’s persistent achievement gap.

Until four years ago, DCPS teachers were left largely on their own in deciding the specifics of what they would teach. To find texts, they worked backward from a set of learning standards that students were supposed to meet by the end of the year.

An English standard might say: “Students will be able to identify the main topic of a multi-paragraph text.” And while standards in social studies and science were more specific, teachers got little guidance on classroom practice.

Even worse, many elementary teachers have focused on skills such as “finding the main idea” in stories or random nonfiction texts. But, research has shown, you can’t understand what you’re reading unless you have background knowledge and vocabulary about the subject matter.

That’s a particular problem for low-income students, who are less likely to acquire knowledge at home. By the time those students get to high school, where they’re expected to understand fairly sophisticated texts, they’re often hopelessly behind their middle-class peers. Fundamentally, the achievement gap is a knowledge gap.

The Common Core State Standards tried to attack this problem by getting schools to build children’s knowledge from an early age. Unfortunately, that aspect of the Common Core has gotten lost in the noisy debate over the initiative’s merits.

That’s partly because the Common Core standards are, in fact, standards and not a curriculum. They were designed for use by schools and school districts nationwide, while curriculum remains a local decision. The Common Core standards suggest texts but don’t mandate content.

Still, DCPS got the idea. Administrators began developing a curriculum rich in science, history and literature beginning in kindergarten. They created “units of study,” six- or seven-week modules on themes such as “Plants are Everywhere” in second grade and “Early Americans” in fourth.

Teachers receive a list of texts that accompany each unit, in the order students should read them. They also get guides for presenting and discussing the texts with students and suggestions for student activities.

These units of study should help DCPS ensure that all students have a common educational experience with the same minimum level of quality. Ideally, the curriculum should level the playing field for students who aren’t acquiring as much knowledge at home as others.

But DCPS doesn’t require teachers to follow the curriculum or use the units of study. Brian Pick, chief of teaching and learning for DCPS, says that 83 percent of teachers report that they use the curriculum. But there is significant variation among classrooms.

It’s unclear from test scores whether DCPS’s efforts are bearing fruit. While students in all categories are improving, according to nationwide tests, the achievement gap hasn’t shrunk, as a recent evaluation of the District’s reform efforts concluded. And reading scores on local tests have largely remained stagnant.

To encourage teachers to use the texts specified in the units of study, DCPS is unveiling an ambitious menu of curriculum-related assignments. For the 2015-2016 year, there will be 215 “cornerstone” assignments, four per year for each grade level and subject. The assignments take only about 10 percent of classroom time, but the idea is to get teachers using the content and teaching it in engaging fashion.

The cornerstone assignments are required. Some are fairly traditional writing assignments or science experiments, while others are more innovative. In third grade, students will create a travel guide to their neighborhoods after studying area monuments and landmarks. Other assignments involve debates or dramatic presentations.

It’s a worthy effort, but it’s too soon to tell how the assignments will play out across the range of DCPS schools or to what extent teachers will embrace them. One cause for optimism — teachers are playing a large role in their creation. This summer, about 100 teachers are developing cornerstone assignments. And teachers will collaborate in evaluating how well the assignments worked after trying them. As Pick recognizes, a curriculum is an eternal work in progress.

“Curriculum-building is like if you were given a rock and told to turn it into a perfect sphere,” he says. “You’re always going to be polishing, refining, making it better, making it richer.”

Too often, education reform efforts are a top-down affair, leaving teachers feeling that things are being done to them rather than with them. If DCPS is open to teacher feedback as it polishes and refines its cornerstone assignments and its curriculum in general, those initiatives could find the kind of reception that will help ensure their success. And maybe the District’s achievement gap will at last begin to narrow.

The writer blogs for and and is on the board of D.C. Scholars Public Charter School and the Writing Revolution.