On average, students in Illinois' charter schools learn significantly more than their peers in regular public schools in both reading and math, a new study finds. But that was not the case for charter schools outside of Chicago, which perform worse in reading and about the same as their regular public school counterparts.
The report, released by Stanford University's Center for Research on Education Outcomes, or CREDO, found that statewide, charter school students receive about two weeks of additional learning gains in reading and a month of additional learning gains in math compared to their regular public school peers.
Black and Hispanic charter school students, on average, experienced no significant learning gains or losses in reading or math compared to their regular public school peers.
CREDO has released several studies that examine the performance of charter schools in individual states, including most recently Massachusetts, Michigan, and Indiana. These individual state reports will serve as the basis for a larger report that will examine the performance of charter school students across 26 states. That report—to be released next Tuesday—will be a follow up to a 2009 study that looked at charters across 16 states.
Digging further into the study of charter schools in Illinois, nearly 41 percent of charter school students there perform worse in reading than their regular public school counterparts, and 37 percent of charter school students perform worse than their regular public school peers in math. The research also suggests that recently opened charter schools have pulled down the average reading gains made by charter school students, prompting concern from researchers that the state's charters' average positive impact may not continue. (This observation comes separately from researchers' findings about the lower performance of charters outside Chicago since such charter schools make up only a very small percentage—9 percent—of charter schools in Illinois overall.)
The report examined test scores for students in grades 3-8 over the course of four years. To compare charter school students' performance to that of their regular public school peers, researchers used a "virtual-control record" in which charter school students are compared to "virtual twins" who attend regular public schools that the charter students would have otherwise attended.
Virtual twins are chosen to match charter school students' standardized test scores, race and ethnicity, special-education considerations, free-or-reduced lunch participation, English proficiency, grade levels, and grade retention in order to compare performance at the two sets of schools.