Graduation rates at almost every Chicago public high school have been revised downward in response to a Better Government Association/WBEZ investigation last year that found Chicago Public Schools routinely miscalculated how many kids made it through senior year without dropping out.

Mayor Rahm Emanuel boasted of rising graduation rates as he campaigned for re-election in 2015. But the BGA/WBEZ investigation found those numbers were inflated – perhaps purposely so – as many principals labeled students as transfers out of the district when they should have been classified as dropouts.

New school-level data provided by CPS – which revisited its rates in response to the BGA/WBEZ findings – show that 4,500 more students dropped out between the 2010-2011 and 2013-2014 school years than was previously reported by the district.

Even with the revisions, more than three-quarters of the 140 or so high schools still saw growth in their graduation rates since 2010, just not as much as originally reported, records show.

Still, the new data show some schools saw significant dips in their graduation rate, especially in the 2012-2013 and 2013-2014 school years where the mislabeling of students appears to be more widespread.

In 2013-2014, for instance, graduation rates at 21 of 139 high schools were revised down by at least 5 percentage points. The biggest decreases were at Southwest Side high schools Curie and Kennedy, and Foreman High School on the Northwest Side. With a combined student population of about 4,500, they are three of the biggest high schools in the district.

Curie’s 2013-2014 graduation rate was revised from 81 percent to 70 percent; Kennedy’s dropped from 65 percent to 56 percent; and Foreman’s slipped from 71 percent to 60 percent.

Graduation rates are based on the number of students enrolled in a school freshman year and the number of students who graduated five years later.

Among the few CPS high schools with virtually no change to their graduation rates were selective-enrollment centers Jones, Northside and Westinghouse.