School vouchers may be the most effective anti-poverty program around, yet they’re fought tooth and hammer by the teachers unions. Late last week the North Carolina Supreme Court awarded a victory to poor kids by protecting vouchers from another union attack.

Two years ago Tar Heel Republicans passed a modest reform offering low-income students $4,200 scholarships to attend qualifying private schools. The law requires, among other things, that private schools report graduation rates and test scores. It also mandates an annual...