Chicago Public Schools students have made the fastest academic progress of the 100 largest school districts in the country, with all racial groups making similar improvements.

That’s according to a new analysis by Stanford University researcher Sean F. Reardon, who told a gathering of Chicago’s educational brain trust Thursday that test scores for the average Chicago student went up by about six grades in the five years between third and eighth grade.

At each grade level, CPS students’ scores also rose faster from 2009 to 2014 than the rest of the nation’s on average, about two-thirds of a grade level locally versus about one-sixth. And the results generally held across racial and ethnic groups, with Hispanic students making even faster progress, said Reardon, using the Center for Education Policy’s database of hundreds of millions of standardized test scores for every third- through eighth-grader in the country.

“Chicago moves from being relatively low-performing even among similar school districts to having test scores that are much closer to the national average,” he told the audience of education experts from the University of Chicago, the Council of Great City Schools, the University of Illinois at Chicago and several foundations. “So that’s remarkably fast, that’s like an extra year of schooling squeezed in somehow between third and 8th grade.”

Elsewhere in the country, he said, as kids progress through school, their score curve generally goes up in affluent districts and down in poorer ones.

Reardon said when he saw the anomaly in Chicago, where students are nearly all low-income, “my first reaction was to be a little suspicious.” Atlanta showed a score bump in 2009 that turned out to be the result of a cheating scandal. But the consistency across race as well as similar growth on a nationally administered no-stakes NAEP test convinced him that CPS’ growth was real and not from a demographic shift in students or from holding lots of kids back a grade.

In his research, Reardon used Illinois State Achievement scores for CPS and its charter students, who are predominantly low-income.

Earlier this week, the state released scores for the PARCC test it has administered for the past few years showing that barely more than one in four CPS elementary students can read, write and do math at grade level. CPS officials have refused many requests to discuss those scores.

CPS Chief Education OfficerJanice Jackson (2nd from right) was at the conference at the Gleacher Center on Thursday. | Rich Hein/Sun-Times

Appearing at the same conference, Chief Education Officer Janice Jackson said the district’s improvements have come during one of CPS’ most tumultuous eras because staffers use data to guide instruction, and because principals have been empowered to lead schools.

“Despite all the chaos, it really took strong leadership at classroom and principal level in order to maintain that,” she said.