So, schools fail 66% of the kids.
Vouchers would allow many parents to send kids to schools which kick out discipline problems and which teach appropriate material. If the school doesn't, the parent can go elswhere. This is the market at work.
I'm guessing that the bottom 33% will stay in rotting government schools and will continue to get inadequate education. I'm also guessing that 66% of the kids will go off and get better education at private schools.
It's better to short-change 33% than to shortchange 66%.
I can't come up with a solution that helps 100% of the kids. Can you?
There's a name for people who want the government to come up with detailed "solutions" for every perceived difficulty any human may encounter.
And that name ain't "conservative."
The beautiful thing about vouchers is the details don't have to be decided by the centralized authority. Because if each aspect of the system has to be planned in advance, it becomes impossible to make progress, as your list of problems so amply demonstrates.
If the elite school is an hour away, there are probably other schools that are closer, that while they are not your first choice, are certainly much better than the marginally performing public schools we have today. As an education consumer, you have to make the best choice between convenience and quality, just like you do when you are choosing anything else in life.
As for additional costs associated with a higher quality education, what is the problem with that? Quality costs more. For people who value a quality education above all else, they will make sacrifices in other aspects of life in order to afford the expenses. Others, who are willing to make do with less, will spend less. Once you accept that people will make rational decisions in the best interests of their children, this becomes a not-unpleasant prospect.
As far as availability is concerned, that is what makes elite schools elite. They will choose the best students they can of the pool that they attract. Schools that are not of quite the same level, but still providing an excellent level of education, will accept students from the pool that remains, and so on down the line. The beauty of this is that each student winds up in a situation that is appropriate for their situation.
As far as teacher pay is concerned, some schools will probably pay more, some will pay less. Teachers will make similar choices of the quality of the teaching environment vs. the rate of pay and convenience, just like everybody else.
And all of these millions and millions of detail are worked out by the people involved, without somebody controlling it all from the top.