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Research Brief


Chicago's "multi-grade" charter high schools (those that include middle school grades) appear to be increasing students' rates of graduation and college entry. The overall performance of Chicago's charter schools in raising student test scores is approximately on par with that of traditional public schools in Chicago. Charter schools in Chicago are not having major effects on the sorting of students by race, ethnicity, or achievement.

Over the past decade, charter schools have been among the fastest-growing segments of the K–12 education sector in Chicago and across the country. In the new RAND report, Achievement and Attainment in Chicago Charter Schools, researchers address several key issues related to charter schools using student-level data provided by Chicago Public Schools (CPS). First, they provide evidence on whether charter schools are attracting high- or low-achieving students and assess the effects of the transfers on racial mix in the city's public schools. Second, they attempt to assess whether charter schools are producing achievement gains for the students who attend them, relative to district-run schools in CPS, as measured by state test scores. Third, they examine longer-term attainment outcomes, analyzing whether Chicago's charter high schools (HSs) are increasing their students' likelihood of graduating, their scores on the ACT® college-admission exam, and their probability of enrolling in college (again relative to district-run CPS schools).

Charter School Transfers

The research team began by examining students transferring to charter schools, to provide purchase on two policy issues relevant to the debate over charter schools. First, do charter schools "skim the cream", serving students who had above-average achievement levels prior to entering charters? The team found that, on average, the prior achievement levels of students transferring to charter schools differ only slightly from the citywide average and from the achievement levels of peers in the district-managed CPS schools they exited.

Second, do charter schools exacerbate or ameliorate racial stratification? The researchers examined how transfers affect the racial and ethnic mix of the charter schools and the traditional public schools (TPSs) that the students exited. They found that transferring students are moving to schools with similar or slightly lower proportions of other students of the same race and ethnicity. In sum, transfers from TPSs to charter schools do not substantially affect the racial mix across schools.

Charter School Achievement Effects in Grades 3–8

The research team gauged the achievement effects of charter schools in elementary and middle grades with a difference-in-differences analysis: For students who have attended charter schools and district-operated CPS schools, the team compared their annual achievement gains in the charter setting and the CPS setting. Consistent with similar studies in other locations, the team found only small differences in average achievement gains between charter schools and CPS schools, and these differences do not point in consistent directions. The only strong finding regarding achievement is that charter schools do not do well in raising student achievement in their first year of operation.

Charter High School Effects On Graduation, College Entry, and ACT Scores

The researchers estimated attainment and ACT effects of Chicago's charter HSs using a quasi-experimental design in which both the treatment group (charter-HS students) and the comparison group (CPS-HS students) attended charter schools in eighth grade, prior to entering HS. This method allowed them to address the selection bias that is inherent in comparing charter students who have chosen their schools with TPS students who may have been assigned to their schools. In this analysis, both the treatment students and the comparison students previously chose charters. In many instances, whether they went on from a charter middle school to a charter HS depended simply on whether their existing charter middle school included HS grades, rather than on a second active choice. Four of the eight charter HSs operating in Chicago during the years included in our analysis were multi-grade charters that included not only grades 9–12 but also grades for younger students (i.e., they served grades K–12, 6–12, or 7–12). Charter eighth-graders who went on to charter HSs were very similar, prior to entering ninth grade, to charter eighth-graders who went on to district-run CPS HSs. Comparing their subsequent ACT scores, graduation rates, and college-entry rates (with statistical adjustments for baseline differences) should therefore provide useful information on how the charter HSs affected those outcomes.

The team found evidence that Chicago's charter HSs may produce positive effects on ACT scores, the probability of graduating, and the probability of enrolling in college—but these positive effects are solidly evident only in the charter HSs that also included middle school grades. For the average eighth-grade charter student in Chicago, continuing in a charter HS is estimated to lead to

  • an advantage of approximately half a point in composite ACT score (for which the median score for the students included in the analysis is 16)
  • an advantage of 7 percentage points in the probability of graduating from HS
  • an advantage of 11 percentage points in the probability of enrolling in college.

The team cannot be sure whether these positive effects are attributable to charter status or to the unconventional grade configurations that eliminate the change of schools between eighth and ninth grade. In one respect, there is no need to distinguish the two possible explanations. Eliminating the middle school-to-HS switch is an inherent part of the educational model of these five charter schools; they have unconventional grade configurations because they are charter schools. The state's charter school policy led to the creation of schools that are producing improved educational outcomes, one way or another.

Nonetheless, the ambiguity about possible interpretations suggests the need for caution in drawing broader inferences for policy. Further research will be needed before anyone can say definitively whether charter HSs produce positive effects in conventional 9–12 grade configurations—and whether district-run schools can produce positive effects by incorporating middle school (and perhaps elementary) grades.

For now, the large, positive attainment results in Chicago suggest promise for (at least) multi-grade charter HSs and demonstrate that evaluations limited to test scores may fail to capture important benefits of charter schools. If charter schools (or other multi-grade HSs) have positive effects on graduation and college entry, they have the potential to make a substantial, long-term difference in the life prospects of their students.

This report is part of the RAND research brief series. RAND research briefs present policy-oriented summaries of individual published, peer-reviewed documents or of a body of published work.

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