Your concerns are reasonable and shared by many others, although as someone who lives in an area where English is almost the exception rather than the rule, your "common conversation" concern is kind of amusing.

Let me clarify something right off: vouchers are a "kludge," a compromise between government controlled schooling and a true free market in education. I don't see them as an ideal solution, and from a purist standpoint do not approve of using tax money to fund ideas I may not agree with, but I'm more realistic than a lot of libertarians, and willing to take what I can get. I see vouchers as a way to give parents more options than they have now, and in surveys a considerable majority of poor and "disadvantaged" parents of school kids feel the same way. Maybe someone should listen to the people who will actually be affected.

Many of your objections fall under the category of "what if the parents make a stupid decision on where to place their kids?" My belief is that most won't. But what if they do? The original post of this thread pertained to a school which I personally felt was not a good educational environment. But basically, as far as these kids and parents go, who the hell asked me for my opinion? The article said the decision to send kids there was voluntary. No kids were shoved in there against their parents' will. Obviously the parents think that this is the best option they have right now. Are they right? Time will tell.

Cream will indeed rise to the top, and like any other competitive industry, this eventually results in better products for everyone across the spectrum. Some people can afford a Jaguar. Most people can't. But almost everyone can afford a reliable and well-built car of some kind. Will there be private school systems that have better records than others? Sure. And these organizations will spread and become available to more people. Or competitors will copy them. Remember that what often sets a good school apart from a bad one is not the buildings, the materials, or other capital, but the teaching methods and curricula, and these can be reproduced and disseminated at almost zero cost. Can't do that with a Jaguar.

You touch on who, if anyone, will control the system, and this is a serious question. Many conservative opponents of vouchers fear, with good reason, the government using this voucher vector to gain control of schools currently relatively free of government coercion. I could easily see the Department of Education reaching for additional power by attaching strings...or hawsers...to the voucher funding. This has to be watched carefully.

Best bet IMO would be for the Federal government to stay out of this, and let the voucher system be handled on a state-by-state basis for now. At least this will spread the bureaucratic damage.

As far as who will set standards, i.e. decide if a school is actually any good or not, well, the customers will. Same as for anything else. Actually, it's easier than with a lot of other things. A school's methods and results are right out there, which makes quality control a lot easier than figuring out if a Jaguar manufacturer is using cheap bolts.