The achievement gap in education between white and minority students has not narrowed significantly since 2004, according to data released earlier this week from a national test of 26,000 students that tracks long-term trends in reading and math proficiency.

Results from the National Assessment of Educational Progress, which the National Center for Education Statistics has published every four years since the early 1970s, show that while young minorities have made academic gains, concurrent improvements in the performance of white students have kept the achievement gap consistently wide.

Among high-school-age students, that gulf translated to a roughly two to three school-year lag in achievement, according to a U.S. Department of Education official quoted in the New York Times.

Despite the persistence of these inequities in academic achievement, “the NAEP results are encouraging news,” said Ronald F. Ferguson, director of Harvard’s Achievement Gap Initiative. “While the achievement gap has not narrowed much, achievement is rising for everybody, which is important from a national perspective.”

“We want to see whites and Asians reach their full academic potential, but we also want to see even more rapid progress among underrepresented minority groups,” Ferguson said. “Our goal should be excellence with equity, but we don’t want to trade excellence for equity. Recent evidence suggests that we’ve made some progress on this long-term journey.”

With the reauthorization of the No Child Left Act of 2001—which aimed to close the racial achievement gap—expected later this year, the Obama administration may see an opportunity to alter the way national education policy addresses the achievement gap issue. Ferguson said there is widespread support for transitioning to a model of accountability that measures relative gains in achievement compared to past years rather than relying on the absolute benchmarks currently in use.

“It is not just about rules or threatening districts with sanctions for poor performance: it’s about creating opportunities for our [ideal] education principles to go into effect,” Ferguson said.

While Cambridge Public School District officials declined to comment specifically on the NAEP results, since staffers had not yet had a chance to review the report, Justin T. Martin, a spokesman for the school district, said he was optimistic about the district’s ability to narrow the achievement gap.

“We recognize there’s a lot to do in closing the achievement gap, but we are encouraged by the tremendous involvement of our community in the effort,” he said.

Cambridge schools—which has a 64 percent minority enrollment, far higher than the 30.1 percent minority enrollment Massachusetts-wide—has seen 3rd, 4th, 5th, and 10th grade scores on the Massachusetts Comprehensive Assessment System state evaluations increase, according to Martin, who attributed the jumps partly to the district’s increased emphasis on reading and literacy.