It would be interesting to see which schools had the voucher students and then to look at the scores of all the students in those schools. Of course, other factors SHOULD be looked at as well, such as parent involvement, overall motivation of the voucher students, behavior, etc.
That's true. If you look at the list of participating schools (especially looking at the schools that actually enrolled voucher students) most of them were Catholic schools and very small religious schools. Some of the smaller schools may not have had very rigorous academic standards to begin with, but Catholic schools usually do.
Even with the voucher program, many of the Catholic schools can't afford to stay in business, more's the pity.
Some of those in D.C. thought that there should have been less focus on vouchers and more on charter schools such as KIPP that were showing great results (although not all charter schools are doing well academically either).