Michigan recently released student growth data showing that many schools in Detroit produce more learning gains for their students than the state average, despite having lower scores overall.

Consider: Detroit Premier Academy’s English growth score this year was 55.  By most other measures, Premier is nothing like the school district in Birmingham, an affluent suburb of Detroit. But in terms of growth, they’re similar: Birmingham’s English growth score was 55.

The Detroit Public Schools Community District has some of the lowest overall test scores of any large urban district, but about 1 in 5 of its schools produced above-average gains in math last year.

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Source: Michigan Center for Educational Performance and Information

To be sure, it matters how much students know, not just how much they grow, said Ed Roeber, assessment director of the Michigan Assessment Consortium, who supervised the state’s testing system for 15 years. But media and policymakers already pay plenty of attention to proficiency, a measure of how many questions students answer correctly on annual exams.

“Readers of newspapers can fixate on inadequate levels of performance, and forget about the improvements that are taking place as well,” Roeber said.

It’s well established in the education world that test scores are closely bound up with poverty. Students from poor families tend to score worse on standardized tests than their peers with more advantages.

Education leaders in Detroit say they prefer to be evaluated based on growth scores. When the Community Education Commission, a group that includes charter school and district leaders in Detroit, gives its own A-F grades to every school in the city, student growth will account for 56% of the grades. The state’s new school grading system also will account for student growth, but it isn’t weighed as heavily.

The math behind the growth scores is complicated, but the basic idea is straightforward.

Imagine two third-graders who score a 100 on the state exam. Two years later, one of the third-graders scores a 250, while the other gets a 300. As a result, the second student gets a higher growth score.

Crucially, the second student would also get a higher growth score than a high-performing peer who started at 300 but only made 100 points of progress.

Emily Gagnon, principal at Detroit Enterprise Academy – which, like Detroit Premier, is run by National Heritage Academies —  said she doesn’t focus exclusively on growth.

But she added that at her school, where every student is considered economically disadvantaged and many are behind academically, growth is a central concern.The schools has posted above-average growth scores in each of the four years that the data has been collected.

Students who fall behind are placed into a separate classroom with additional teachers and learning materials tailored to their needs, Gagnon said.

“We know we have a lot of students with low socioeconomic status,” she said. “But that doesn’t deter teachers from moving my students academically.”