The old, worn out arguments are shallow beyond belief.
1. We take money away from public schools.
Yeah. But a school with half as many kids is no longer 'overcrowded'. The bad section of the school can be shut down. Ideally, they would realise that tenure is not as important as which teacher is doing a better job [note ideally] and they could lay off the ineffective teachers. So not only are the costs at 1/2, but they have an opportunity to improve their school at the same time. If they blow that opportunity, the parents will choose to give up on that school.
2. Parents will be out-of-pocket more in private schools.
That is an odd argument since the average cost of private schools is lower than public, that is if you have religious based schools.
It is unconstitutional. What we have right now is unconstitutional. This, at least, promotes freedom.
BTW, this is also a look ahead at what universal medical care will be like in urban settings.