The debate over charter schools shows few signs of receding as a central component in the discussion about improving U.S. public education. While proponents see charter schools as a vital source of innovation in public education, opponents feel they are largely ineffective and operate at the expense of large numbers of students. To complicate matters, previous research about the impact of charter schools on student achievement has uncovered mixed results.

A 2011 study from MIT for the National Bureau of Economic Research, “Explaining Charter School Effectiveness,” collects results from more than two dozen Massachusetts charter schools to examine the “heterogeneity in the effects of charter schools across demographic groups and between urban and non-urban areas.” The researchers — Joshua D. Angrist, Parag A. Pathak and Christopher R. Walters — examine data from 2001 to 2010 provided by schools relating to students’ race, gender, class and standardized test scores, among other factors. The study also looks at differences between schools that grant student slots by lottery and those that are open-enrollment.

The study’s findings include:

• Charter schools in urban areas raised achievement levels well beyond those of other non-charter urban schools and even helped students exceed non-urban achievement levels in math. The data show that urban charter schools are “most effective for minorities, poor students, and low baseline achievers, so part of the urban charter advantage can be explained by student demographics.”
• By contrast, charter schools in non-urban areas did not boost achievement in either English language arts (ELA) or math, and even resulted in lower student achievement than traditional non-urban public schools in some cases.
• Among urban charter schools, larger standardized test score gains were realized by those schools that were over-subscribed that had well-documented lottery records as compared with “under-subscribed urban charter schools with poor lottery records.”
• The authors conclude that the effectiveness of over-subscribed urban charters, as compared to under-subscribed ones, is due to the fact that they typically employ a “no excuses” approach to education. Its characteristics include an extended school day, a strong focus on discipline and a traditional curriculum centered on reading and math skills.

The authors conclude that the “large negative estimates of non-urban charter impacts reported here raise the question of why, despite their unimpressive achievement effects, many of these schools are over-subscribed. One possibility is that parents misjudge the consequences of non-urban charter attendance…. It’s also possible that non-urban charter schools generate gains that non urban families value more than the skills measured by the MCAS, especially in view of the fact that most non-urban students do reasonably well in any case.”

The study also notes that more established charter schools were found to have better results in terms of student achievement as compared with newer schools. In addition, schools that began as charters were found to have better results than those that started as traditional public schools and later became charters.

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