Recent studies purport to show that voucher programs result in better achievement by black students at private schools, and that vouchers motivate public schools to improve. Those results are overstated, a new analysis argues.
Martin Carnoy, a Stanford University education and economics professor, reviewed two voucher studies for the Economic Policy Institute, a labor-backed think tank.
The first study involved recipients of privately funded vouchers in New York City, the District of Columbia, and Dayton, Ohio. Paul E. Peterson, a prominent voucher researcher and a professor of government at Harvard University, found last year that black students using the vouchers outperformed a control group made up of students who had applied for vouchers but remained in public schools.
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|The report, "Do School Vouchers Improve Student Performance?," is available from the Economic Policy Institute. (Requires Adobe's Acrobat Reader.)|
Mr. Carnoy argues in the new analysis that Mr. Peterson and his colleagues failed to account for a "disappointment effect" on the nonvoucher students. The difference in achievement results may have more to do with "lower gains by discouraged voucher rejectees rather than greater gains by recipients," he writes.
The second study Mr. Carnoy examined was released earlier this year by Jay P. Greene, senior fellow at the Manhattan Institute. Mr. Greene found that low-performing Florida schools facing the prospect that their students would receive vouchers to attend other schools made significant gains on state achievement tests.
Mr. Carnoy said the study failed to account for other possible causes of the improvement by the failing public schools.
"The 'scarlet letter' effect from identifying low-performing schools is as plausible an explanation for the test score gains as is the voucher threat," he writes.
Mr. Peterson defended his research last week.
"It's always nice to have people think of potential ways one could improve one's research," he said. "I still think we have the very best possible research design."
Coverage of research is underwritten in part by a grant from the Spencer Foundation.
Vol. 20, Issue 37, Page 8