This is a rather long post, so I'll just focus on quoting this part.
Even private schools "live off the teat" of the tuition of the students attending, and wouldn't be any more likely to kick out students. I'll point out three quick conclusions that I think you're drawing:
1. The fault in the schools lies with the disruptive students. Even great teachers can't be good when they're being policemen.
2. These disruptive students tend to come from economically disadvantaged families.
3. It is the high concentration of disruptive students that makes schools bad.
When you leave school quality up to the market, you will have the same outcome. The rich will be able to afford good schools. The poor will remain concentrated in bad schools, and you will still have large numbers of disruptive students in bad schools.
I think your speculating, as private schools do remove students and usually have long waiting lists to refill the spots vacated by expelled students. They would never be reliant on government "Teat" money, unless their system of education, discipline, and curriculum was unfavorable to parents. The drop-out rates at private schools hardly support your argument, as again, waiting lists can be long to get into them. There must be some reason for the waiting lists.
I have had years of private school experience with the raising of my own children, and the experience of conversing, sharing and learning from other private school parents.
The only problem I see with the voucher system is this:
Whenever uncle sam or a state government gives us back our tax money for anything, they really hook-on the strings of control if they can. Private schools that receive government vouchers will most likely be watched closely by the state authorities to make sure that the voucher money is being utilized fairly, and ethically.
That's ok, but if the State entities start mandating the curriculum then we're back to step one........we just have glorified public schools again. Although maybe there should be a certain curriculum standards to be covered, and then the private schools can offer other choices beyond those basics/standards if they choose.
If parents want to use the voucher money to educate their kid in a Catholic, Islam, or non religious school, fine and dandy. If Uncle Sam expects certain safety code, standards with giving back the tax money, fine, but just don't mess around with the curriculum in the area of ethics unless, a virulent anti-american or anti-social curriculum is being taught.
I can see why so many parents are resorting to home schooling. Even home schooling groups are around so that these kids get socializing with others of their peer groups too. This includes recreational activities, trips to historical places, museums, etc. Socializing as been one of the main critiques of the anti-home schooling element.
Also the teacher's unions are very anti-voucher, and anti-home schooling. Ever checked into their reasons? You might be surprised.
People who "poo poo" home schooling don't realize what a massive committment a parent or parents must make for this method of education to work. If done correctly these home school kids constantly score higher than the national average for their age, and grade group. Home schooling shouldn't be attempted if a parent can't be at home full time, or they lack the skills to work the system in a way thats satisfactory. If kids that our home schooled do not score within their mean national average and our not doing well, then maybe they need to be put in another education system. Not all of us parents are cut-out to be teachers. It's nothing to be ashamed of, it's just a fact. To just isolate your kid for social reasons and not for educational advantage might not be such a good idea either. Of course there are exceptions to every situation. Some kids may do good in home schooling because they are handi-capped physically, mentally or emotionally, and with a loving parent's committment,
may do far better than in a special Ed class in the public school environment.
Discipline and respect for authority, and accountability, taught at home will make for better education environments at all of our public schools, regardless of their geographic locations, i.e. minority areas, low income areas.....etc. Then teachers can be teachers.