Letter from a teacher: http://whitegirlbleedalot.com/letter-teacher-3/
I see the legislature’s fiscal point. States and districts rely on the tax contributions of residents who don’t use the public schools to fund the system for those who do. If they begin spending $5,000/year on additional students, that’s an additional cost. On the other hand, if a public-school student switches to private, that’s a possible savings, because the per-pupil cost of public schools is less than $5,000.
They’re really asking parents to enroll in public school for a year, because attempting to transfer to private school more than halfway through the year is unlikely to fly. I suppose what they really wanted was to offer the vouchers only for public-to-private changes, but couldn’t swing that politically.