In June, Illinois Gov. Bruce Rauner called some Chicago Public Schools "crumbling prisons," and then five-year-old emails from when he was in private business revealed he’d also called principals "managerially incompetent" and half its teachers "virtually illiterate." Chicago Mayor Rahm Emanuel could not let the moment pass, even as he said he was accepting Rauner’s apology for the remarks.

At a press event after Rauner’s email comments were released, Emanuel used the opportunity to boast about CPS students’ achievements. "Well, let me tell you what the [Chicago Public Schools] ‘crumbling prisons’ with wardens as principals and guards as teachers have done. They lead the country in high school graduation of an urban school system…They now match the United States of America in kids graduating high school going on to a four-year college...That same prison with that same warden and that same security guard is also producing eighth-grade leaders in the country in math gains, fourth-grade leaders in reading gains."

That’s a lot to study, so we decided to do our homework.

Testing the claims

Lauren Huffman, a spokeswoman for the mayor’s office, noted Emanuel often repeats those claims, citing statistics from the National Assessment of Educational Progress. The NAEP calls itself the largest, continuing organization that tests students in a variety of subjects. It is under the umbrella of the National Center for Education Statistics run by the federal education department.

We were able to verify the mayor’s claims about eighth-grade math and fourth-grade reading by examining "The Nation’s Report Card" for 2016 and the Trial Urban District Assessment published by the NAEP, and by interviewing Grady Wilburn, a statistician with the National Center for Education Statistics.

Wilburn said Chicago’s fourth-grade reading score had improved 15 points since 2003, the second-highest improvement behind Washington, D.C., which improved 26 points. Since 2013, Chicago improved 7 percentage points and tied for first place with Washington, Cleveland and Boston.

While the chart shows numerically that D.C. is higher, it does not account for statistical significance. Wilburn said when districts are tested for statistical significance, Washington, Cleveland and Chicago are not different from each other. Significance testing considers sampling error associated with only assessing a portion of students, not all of them.

In eighth-grade reading, Wilburn said scores show Emanuel’s statement to be accurate.

Since 2003, he said, eighth-grade CPS math scores have improved 20 percentage points. They are statistically tied for highest gains since 2003. They’re tied with Atlanta, Boston and Los Angeles.

If you look just at 2013-15, Chicago’s scores went up 6 percentage points, and that is the biggest gain. Of the 21 urban districts monitored, CPS students were the only ones to improve in eighth-grade math from 2013 to 2015.

Passing or surpassing?

Emanuel made two other claims about Chicago Public School students. One of the claims was that they now match the nation in kids graduating high school and going on to a four-year college.

The Chicago Consortium on School Research at the University of Chicago published a new study in June that examined high school graduation, college enrollment and bachelor’s degree attainment rates.

Chicago Public Schools’ "four-year college enrollment rate for 2014 is 42 percent, two percentage points lower than the national rate, and half of CPS graduates who enroll in four-year colleges will graduate in six years," a summary of the report says.

Two percentage points lower than the nation in college enrollment would indicate Emanuel’s statement is slightly off, but it is clear CPS graduation rates, college enrollment and degree attainment have been rising significantly. In 2006, the graduation and college enrollment rate was eight percent. In nine years, by 2015, that rate had doubled to 16 percent.

Emanuel’s other claim, that CPS leads the nation among urban districts for high school graduation, was more difficult to verify. The National Center for Education Statistics put the adjusted cohort graduation rate at 82 percent for 2013-14. Jenny Nagaoka, deputy director of the University of Chicago Consortium on School Research and an author of the study of CPS college attainment, said the CPS rate for the same year is 74 percent, but she cautioned the two institutions might rely on districts that calculate rates differently.

Unlike reading and math scores, there doesn’t appear to be a comparison of urban district graduation rates. In 2012, she said CPS was "probably in the middle of the pack" nationally.

"On the basis of this, I can’t conclusively say this is a true or false statement," she said. "CPS is certainly higher than Baltimore. We may be higher than New York. CPS is certainly higher than many. Chicago has made great gains. We’ve really closed the gap compared to the national rate and that’s important."

Chicago’s improvement in graduation rate comes at a time when, nationally the rate also has been climbing. "It is a big accomplishment to improve the gap when the national rate also is improving," Nagaoka said.

Our ruling

Emanuel’s boasts about reading and math scores compared to other urban districts were accurate. His statement about going on to four-year college was a bit off, but probably not statistically significant. We could not find data to conclusively verify that CPS leads urban districts nationwide in its graduation rate, but it has made dramatic improvement.

A similar study from the consortium concludes, "While changes in student demographics account for some of the increase in graduation rates, improvements in student performance in high school — compared to similar students who started high school in the past — accounts for most of the change; students are passing more classes and earning more credits in ninth grade. Not only are more students graduating, but they are leaving high school with higher achievement than graduates in prior years.

We rate this claim Mostly True.