Last week’s OPPAGA report on corporate tax credit vouchers got a double-barrelled blast of criticism today. Kevin G. Welner, director of the Education and the Public Interest Center at the University of Colorado at Boulder, argues in this op-ed in the Orlando Sentinel that OPPAGA’s report – which concluded vouchers were saving the state money – is based on “numbers out of thin air.”

The report assumes 90 percent of CTC voucher students would have attended public schools had they not received a voucher. “The defense of this guess is tucked away in the report’s appendix,” Welner writes. CTC vouchers “are available only to low-income students, so according to the report, it’s ‘reasonable to assume a high percentage of low-income students would not be able to afford private school without a scholarship, and therefore, would attend public school in absence of the program.’ But the reality is that Catholic schools in urban areas sometimes enroll 60 percent to 70 percent low-income children.”

On his blog, USF Professor Sherman Dorn cites Welner’s piece, riffs in more detail on the fixed-cost argument and concludes, “Essentially, the analysis is a simplified (and data-thin) calculation of the impact on state government, not the impact on total revenues and services.”