Matt Barnum and Alicia A. Caldwell:

When Doug Ducey signed an expansive and unprecedented school choice law as Arizona governor last year, he pitched it as a way to help students escape struggling public schools.

“Our kids will no longer be locked in underperforming schools,” Ducey said in a statement at the time. “We’re unlocking a whole new world of opportunity for them and their parents.”

But since Arizona became the first state to allow any family to use public funding for private school or home schooling, students who had already opted out of public schools have been among the biggest beneficiaries. Data from a few other states that have since enacted similar programs show the same trend.

These findings have been seized on by critics who say these programs are draining resources to support middle- and-upper-income families who can afford private education.

“It’s money that was on the table for public schools,” said Beth Lewis, executive director of Save Our Schools Arizona, a leading opponent of the state’s choice program. “We’re now propping up an entire other school system.”

Supporters of these voucherlike programs, including private-school parents and many Republicans, say they are working as intended: They fund whatever type of education families want, both for students who have left public schools and those who never attended one.