It's all about Oreo cookies. :) According to Steve U., if we have a switch rate over 1%, we'll save money with the voucher system. Money saved means more money available to allocate to public schools. But suppose that we DON'T see a greater than 1% switch rate. In this case the voucher program will "lose money." I have to put that in quotes, because I don't think paying for education is losing money.
You see, ANY switch rate, no matter how small, will mean fewer children in public schools and more resources available per student. (That's true even if we end up spending more money from the general fund on this voucher experiment.) It is in our best interest to encourage people to take children out of the public schools if they are able to bear that burden. It really can benefit all the children who remain. Anybody chanting the chorus of "smaller class size" should concur with this argument.
It may be true that vouchers won't help poor kids get into private schools. Many budgets are just too tight to spend extra money for things that could be had for free in the public system. But suppose the voucher is the needed incentive to get 1% of rich people currently in public schools to switch to private schools. Voila! We will then reach the point where the vouchers are a net financial gain for the public school system. At that point, we're actually helping ALL the public school kids, poor or rich.
We do lots of things with taxes to create incentives for businesses. We do this not because we want to subsidize the business, but because we want to incentivize behaviors we like. We want businesses to server people in poor areas. We want businesses to build in struggling parts of the city. None of these incentives are inappropriate for a local government in my view.
The argument that we shouldn't give vouchers to rich kids--even when doing so will help poor kids--is to cut off our nose to spite our face. I'll be voting in favor of referendum 1.