The notion that capitalism competition will improve schools is misguided, and will probably contribute to an ongoing problem of an increasing divide between rich and poor. If vouchers can be used for priviate schools, the rich who are already paying for private schools will get a subsidy rather than contributing to the common good, and everyone who can flee public schools by means of talent or money will use vouchers to escape standard, non-chartered public schools, making the overall quality of public schools for most citizens far worse. The end result is also segregation of school, with the poorest and the weakest students caught in a downward spiral.
I am very suspicious of vouchers for anything. The vouchers have to be accepted, and it can easily happen that the better schools, and then the somewhat inferior schools, won't accept the vouchers, either because they want higher tuitions or because they are fully booked. And parents will go running around with their vouchers and find them to be like Confederate money. Maybe this isn't supposed to happen. Maybe it won't happen, or won't happen for a while. But I am very suspicious of vouchers just the same. Maybe what would happen would be that people with vouchers would have to pay additional cash out of pocket (either on the table or under the table) to make up the difference between what the school wants and what the voucher is good for.
In most aspects of our lives, we select things that have become successful through competition in the marketplace. We rely on this mechanism to bring us everything from good food to high quality and safe cars. In other words, we trust the market in many, many ways.
This brings us to a fair rationale for school vouchers. When it comes to education, there is much less competition. There is only one public school system in a given place and students are generally assigned to a school. If we were to adopt a voucher system, the argument goes, we would force public schools to compete with private schools and perhaps with one another. This would, advocates say, improve the performance of public schools.