Tiffany McLeary, 16, of Silver Spring, a student at Bethesda Chevy Chase High School, holds Amayah Varfley, 3, of Germantown on her shoulders during a March to Close the Gap rally on April 27, 2014. (Sarah L. Voisin/The Washington Post)

A new study using federal data finds that black students who attend schools that have a majority of black students score lower on achievement tests than black students who go to school with fewer other black students.

The findings held true after researchers accounted for family income, level of parent education and other factors they thought might impact how students perform on tests.

And they were particularly strong for black males — test scores for black female students were fairly consistent whether they attended schools with many other black students or schools with relatively few, researchers found.

The study, conducted for the U.S. Department of Education’s National Center for Education Statistics by the American Institutes for Research, analyzed the test scores of 100,000 eighth-graders on the 2011 math portion of the National Assessment of Educational Progress, also known as NAEP.

The overall black-white achievement gap on the NAEP 2013 math test for eighth-graders was 31 points — equivalent to three years of schooling. That gap has not changed from 2007 to 2013.

Researchers looked at how black students performed on the test and the demographic makeup of their schools. A “high density” black school was defined as a school where at least 60 percent of the students are black. Nationally, these schools were concentrated in Southern and Midwestern cities, researchers found.

The researchers adjusted the test scores for all the factors they thought could affect student achievement, including family poverty, concentration of poverty in a school and credentials of teachers, and they still found the achievement gap between average white males and black males attending a “high density” black school was 25 points, compared to a gap of 17 points for black males who attended schools where blacks made up 20 percent or less than the student body.

“We controlled for all the things that we thought might make a difference and we saw that for black males in the highest-density category, their achievement is significantly lower than for those in less density,” said George Bohrnstedt, an institute fellow at AIR and one of the authors.

The findings come amid increasing evidence that many public schools are resegregating, with some research suggesting that U.S. public schools are as segregated by race now as they were in the 1960s.

The AIR study did not look at causes behind the achievement gap between black males in schools with a “high density” of black students and those at “low density” schools.

But Bohrnstedt offered several possible explanations. Schools with large percentages of black students, often high-poverty schools, are more likely to be staffed by less experienced teachers, research has found. And social scientists theorize that some black students adopt an “oppositional culture” in which they reject academic success as “acting white.”

Other researchers have found that teachers in schools with large numbers of black students tend to expect less of them, which may result in less engagement on the part of both teachers and students. Finally, black male students are disciplined at higher rates than their non-black peers, leading to more frequent out-of-school suspensions and higher dropout rates.

“We know from research that the newest teachers with the least experience end up in the most difficult schools and very often, their expectations for black students aren’t as high as for others, and that’s especially true for black males,” Bohrnstedt said.

Concern about the outcomes for young black males is at the heart of the Obama administration’s initiative known as “My Brother’s Keeper” and is a reason why some urban school systems have moved toward boys-only schools. In January, D.C. Chancellor Kaya Henderson announced a $20 million program designed to support black and Latino males, including opening an all-boys college preparatory high school east of the Anacostia River in 2016.