VOUCHER STUDY’S APPROACH AND OUTCOMES QUESTIONED
Review concludes that positive tests-score effects of voucher competition on Milwaukee public schools are very small at best
EAST LANSING, MI (May 18, 2009)—A recent report contends that competition from Milwaukee’s private school voucher program for low-income families has benefited Milwaukee public schools. A Think Twice review of that report raises a number of questions about its statistical methods and concludes that any positive effect of competition is very small, if it exists at all.
The report, The Effect of Milwaukee’s Parental Choice Program on Student Achievement in Milwaukee Public Schools, was written for the School Choice Demonstration Project at the University of Arkansas. It was reviewed for the Think Twice think tank review project by Gregory Camilli of Rutgers University, an expert in the use of statistics and measurement in social science research.
Camilli points out that the largest competition benefit emphasized in the report was obtained with no controls, but also that these benefits were small from a practical perspective. Moreover, when statistical controls are used, no statistically or practically significant competition benefits were found. Those controls essentially account for whether there is in fact private school competition for a public school student (that is, the effects of grade and year are distinguished from the effect of competition).
Despite the questions Camilli raises about the report, he commends it for clearly and thoroughly presenting its findings and for presenting its methods and statistical models clearly.
Camilli concludes, “Before the results of this study can effectively inform the decision of whether to expand or reduce the size of the voucher program in Milwaukee, a number of issues need resolution. Most importantly, the use of uncontrolled estimates requires justification.”
Find Gregory Camilli’s review on the web at: http://www.greatlakescenter.org.