I'm doubtful about your assertion that new schools will pop up. I actually doubt that they will, especially in poorer areas. So the kids whose parents are able will leave, taking their money. Thus solidifying the problem of funding to the schools.

And, as mentioned, transportation is a big issue for many as well. School busses are nice for those parents who have to work at 7, or earlier, and can't take their kids to school. Same going home. Unless, of course, you're going to start bussing kids to all the new schools that pop up, assuming any do.

Also, how do you deal with regulations and standards? If my tax money is going to a private school, it better follow a standard and not be teaching creationism, etc.

And I, too, would like to see your source on cost of education... You also assume that the private schools won't all be owned by the same company or that they won't agree to set prices the max available from the vouchers... Or higher.