D.C. Public Schools Chancellor Kaya Henderson in November 2012. (Katherine Frey/The Washington Post)

D.C. Public Schools posted larger gains on 2013 national math and reading tests than any other major urban school system, but the District’s performance continues to trail the large-city average, according to a federal study released Wednesday.

The D.C. Public Schools (DCPS) system also continues to have the nation’s widest achievement gaps between white and black students and white and Hispanic students, according to the study, which shows that poor black children in the District continue to score lower, on average, than their counterparts in other cities.

The study is based on the 2013 National Assessment of Educational Progress, math and reading tests that are administered every other year to a representative sample of fourth- and eighth-graders across the country.

The District’s gains — which reflect only the performance of traditional schools, excluding charter schools — come amid a period of rapid change that has made the city a nationally watched experiment in improving urban schools. Public preschool is now available to all children; the city has adopted new academic standards; demographics have shifted; and the traditional school system has gotten rid of teacher tenure, instituting evaluations that tie job security and pay to student test scores.

It’s difficult to say exactly how those different factors have contributed to the city’s gains, but Chancellor Kaya Henderson said the growth is evidence that the school system’s key policies are the right ones.

D.C. Public School fourth-graders improved in both math and reading since 2011, but average scores lag behind other large urban school systems. (The Washington Post/Source: National Center for Education Studies)

“We’ve raised the bar for students; we’ve raised the bar for teachers; and they have risen to the occasion,” said Henderson, speaking alongside Mayor Vincent C. Gray (D) at a John A. Wilson Building news conference Wednesday afternoon. “The results from his test show that the things we’re doing in DCPS are working.”

Gray echoed that message, citing the public pre-kindergarten programs he has championed as an underlying reason for the gains. “The investments that we’ve made and the strategies that we’ve deployed, we think, are paying off and have paid off very well,” he said.

The school system’s progress mirrors citywide results released last month, which showed significant gains — among the District’s largest in the history of the national exams. Those results included D.C. charter schools, raising questions about how much the traditional school system — which has struggled to retain students in the face of charter competition — contributed to the growth.

The data released Wednesday, combined with additional data provided by the National Center for Education Statistics, show that DCPS gains equaled or exceeded those of D.C. charter schools in each tested subject and grade level.

Education Secretary Arne Duncan singled out the District and two other cities, Los Angeles and Fresno, Calif., for their significant gains. These cities are “great examples for the rest of the country of what can happen when schools embrace innovative reforms and do the hard work necessary to ensure that all students graduate ready for college and careers.”

The data released Wednesday show that overall, achievement in large cities grew slightly faster than that of the country as a whole but continued to lag behind the national average.

The tests are scored on a scale of 0 to 500 points. Overall, urban school systems averaged gains of between one and three points between 2011 and 2013, continuing a decade of steady if incremental growth. But some cities stagnated while others slid backward, and achievement gaps generally did not budge.

“We must do more collectively to ensure that our minority students are achieving at high levels,” Duncan said.

The District’s school system was the only city to make statistically significant gains in both subjects at both grade levels, posting gains of five to eight points. Still, while Washington is no longer dead last among large cities, it is still in the bottom half, its scores tying or surpassing those of four to nine of the 21 participating cities.

The proportion of students who scored high enough to be considered proficient or advanced also trailed the big-city average. Among fourth-graders, one-fourth were proficient or above in reading and one-third were proficient or above in math.

The gains mask enormous achievement gaps in the District between black and white students — gaps that are about double the national urban average and are larger than those in every other big city, including New York, Chicago and Miami.

In fourth-grade reading, for example, black students averaged a score of 192 compared with white students’ 260, a difference of 68 points — four points larger than in 2011 and more than double the average urban gap of 34 points.

White students in the District scored higher than white students in any other large city. More than three-quarters scored high enough to be deemed proficient in fourth-grade reading, while only 13 percent of blacks and 26 percent of Hispanics met that mark.

Gaps between poor children and their more affluent peers also widened in 2013, although it’s difficult to interpret that shift because the way poor children are identified has changed since 2011.

The overall gains come amid demographic shift in the District that is beginning to trickle into the schools.

The proportion of white fourth-graders has approximately tripled over the past decade, to 13 percent, while the proportion of black students has fallen from 87 to 67 percent over the same period.

Michael Casserly, executive director of the Council of the Great City Schools, an organization of urban school systems, said that demographics alone cannot account for the District’s growth. Subgroup data and the council’s analysis show that black students and Hispanic students made gains, he said. “Our takeaway is that all of the groups contributed to the growth, not just whites,” he said.

Henderson — who serves as a member of the executive committee that governs the Council of the Great City Schools — also pushed back forcefully against the idea that demographic changes contributed to the growth. “The gains are true gains,” Henderson said.

Charter schools, which enroll 44 percent of the city’s students, outperformed the school system by significant, double-digit margins in eighth-grade math and reading.

But the two sectors posted virtually the same average scores in fourth-grade math and reading, with the school system besting charters by just one point in both subjects.

The two sectors also made similar gains in every subject except eighth-grade reading: The school system gained eight points, while charters gained only two.

However, charter schools’ black students, as well as charters’ poor children and students with disabilities, scored higher on all exams than their counterparts in the traditional school system. Charters’ Hispanic students scored higher on three of the four tests. Scott Pearson, executive director of the D.C. Public Charter School Board, said those results are heartening.

There aren’t enough white students in charter schools to measure their achievement separately, so it’s not possible to judge the size of charter schools’ achievement gaps.

“We don’t have as many white kids, we don’t have as many high-income kids, so our overall comparison doesn’t look as strong,” Pearson said. “But we’re actually showing a lot of growth in the subgroups.”

Mike DeBonis contributed to this report.