Replacing the city’s Specialized High School Admissions Test wouldn’t significantly increase the diversity of the eight sought-after schools that use it, and could exclude even more black students, according to a new report.

The report from the Research Alliance for New York City Schools challenges the rationale behind Mayor Bill de Blasio’s interest in replacing the exam with a broader set of admissions criteria as a way to increase the share of black and Hispanic students at the specialized high schools. In 2014, just 11 percent of the offers to those schools went to black and Hispanic students, though they made up about 70 percent of the city’s eighth graders.

“Maybe it was naive, but I thought if you switched to more holistic measures, it would diversify the admissions pool considerably,” said Sean Corcoran, a New York University researcher who co-wrote the report. “It turns out that students disproportionately offered admission to specialized high schools are the same students who get high scores on the state tests and get high grades.”

Supporters of the current admissions system have long pointed out that many of the city’s screened high schools, which look at factors like attendance and school grades when making admissions decisions, have a higher percentage of white students than the specialized schools. But there has been little information available about what would happen if Bronx Science, for example, switched to a similar system.

To find out, the researchers simulated admissions scenarios with varying combinations of state scores, school grades, and attendance criteria using Department of Education data from 2005 to 2013. Using those criteria instead of the test, the researchers found, would tip the scales in favor of girls, who made up just 42 percent of students in the specialized high schools in 2013-14. Nixing the test would also increase the share of white students and Hispanic students admitted, reduce the share of Asian students, and in some cases reduce the share of black students, too.

They also found that a little more than half of the students admitted under those rules were the same students admitted using the SHSAT, “suggesting there is considerable overlap in students who would be admitted under different rules.”

“While there are some changes under these new methods, it’s not that earth-shattering,” Corcoran said.

If the criteria were to change, though, many students would probably also change their behavior and focus their efforts on grades or attendance, something their findings can’t account for, the researchers note. Their simulations also don’t account for qualitative factors like essays that could be a part of a revamped admissions system.

Still, the findings are clear enough to become a potential roadblock for the de Blasio administration’s effort to push admissions-policy changes. Even discussions of changes have provoked protests from a number of alumni groups and alarmed elected officials who represent neighborhoods with high proportions of Asian students. Meanwhile, state legislation addressing the issue — which would be necessary to change the admissions policies at three of the eight schools — has languished for years.

Just 6 percent of eighth graders who go through the high school admissions process get an offer from a specialized school, but those schools take up a disproportionate amount of the debate about admissions and enrollment because of the long records of schools like Stuyvesant and Brooklyn Tech of preparing students for success. If the central argument for eliminating the test turns out to be less than clear, support for sweeping changes could erode further.

“Today’s report highlights some significant challenges, but we remain committed to achieving our goal of having specialized high schools reflect the great diversity of our City,” department spokesman Harry Hartfield said in a statement.

Still, the report notes that there are other ways the city could help black and Hispanic students, girls, and members of other underrepresented groups claim more seats. Among students who scored equally high on state tests in seventh grade, students eligible for free lunch, girls, and Latino students are less likely to take the specialized high school test at all. And once they earn a seat at one of the schools, girls are 11 percentage points less likely to accept it.

Those numbers show that programs to encourage high achievers to prepare for and take the test could have a positive effect.

Hartfield said the city is continuing to analyze the data and expand access to free test prep. In December, officials told City Council members that they are asking all middle school guidance counselors to push the top 15 percent of their students to sign up for the SHSAT.

“We cannot have a dynamic where some of our greatest educational options are only available to people from certain backgrounds,” de Blasio said last year.