I couldn’t tell you because I’m not aware if any statistics are available to the public.
These are some of the statistics:
Joshua Cowen, “School Choice as a Latent Variable: Estimating ‘Complier Average Causal Effect’ of Vouchers in Charlotte,” Policy Studies Journal, November 2007.
Charlotte, NC—After one year, voucher students had reading scores 8 percentile points higher than the control group and math scores 7 points higher.
Alan Krueger and Pei Zhu, “Another Look at the New York City School Voucher Experiment,” American Behavioral Scientist, January 2004.
New York, NY—The voucher students had higher scores, but the results did not achieve statistical significance. Subsequent analysis has demonstrated that this occurred because the study used inappropriate research methods that violate the norms of the scientific community; if legitimate methods are used, the positive results for vouchers become significant
John Barnard, Constantine Frangakis, Jennifer Hill, and Donald Rubin, “Principal Stratification Approach to Broken Randomized Experiments: A Case Study of School Choice Vouchers in New York City,” Journal of the American Statistical Association, June 2003.
New York, NY—After one year, voucher students had math scores 5 percen¬tile points higher than the control group.
William Howell and Paul Peterson, The Education Gap, Brookings Institution, 2002.
Washington D.C.—After two years, black voucher students had combined reading and math scores 9 percentile points higher than the control group.
William Howell and Paul Peterson, The Education Gap, Brookings Institution, 2002.
Dayton, OH—After two years, black voucher students had combined reading and math scores 6.5 percentile points higher than the control group.
William Howell and Paul Peterson, The Education Gap, Brookings Institution, 2002.
New York, NY—After three years, black voucher students had combined reading and math scores 9 percentile points higher than the control group.
Jay Greene, “Vouchers in Charlotte,” Education Next, Summer 2001.
Charlotte, NC—After one year, voucher students had combined reading and math scores 6 percentile points higher than the control group.
Cecilia Rouse, “Private School Vouchers and Student Achievement,” Quarterly Journal of Economics, May 1998.
Milwaukee, WI—After four years, voucher students had math scores 8 NCE points higher than the control group. NCE points are similar to percentile points.
Jay Greene, Paul Peterson and Jiangtao Du, “School Choice in Milwaukee: A Randomized Experiment,” in Learning From School Choice, eds. Paul Peterson and Bryan Hassel, Brookings Institution, 1998.
Milwaukee, WI—After four years, voucher students had reading scores 6 Normal Curve Equivalent (NCE) points higher than the control group, and math scores 11 points higher. NCE points are similar to percentile points.