In 2014, there 250,000 students participating in voucher programs. The expected graduation this school year is 3.2 million from public schools in the US and 300,000 from private schools. Unless we're not on the same page, there are over 10 times as many students graduating from public schools as there are vouchers issued in the US.
Fast Facts
School voucher - Wikipedia
But not with charter schools though. This is less of an issue of what does better as a whole than it is individual choice. You can go to areas (middle-class and upper-class suburbs) where the public schools have a fine history. We used to have that here where I live. Then pin that up against private school to get desired results. You won't get the same results if you put lower income city public school against private, and lower income schools are where most of those voucher kids are going to come from.
Charter Schools are nothing like private schools. Charter Schools are independently operated public schools started by parents, teachers, community organizations, and for-profit companies. These schools receive tax dollars, but the sponsoring group may also come up with private funding. Charter Schools do not charge tuition. They are also subject to most of the same laws and regulations that govern public schools. Unlike private schools, they are subject to the same disclosure requirements as public schools which include test scores, facility qualifications, and statistics related to discipline and crime. Most states require the same minimum level of training for teachers in Charter Schools as in public schools. Another difference is that most Charter Schools unlike private schools are usually specialized. For example, there are high school charter schools that specialized in math and science or the arts and there are those that cater to children of homeless parents, ESOL students, gifted students, students with learning disabilities and dropouts. Charter Schools are similar to private schools in that they have freedom in regard to curriculum and teaching methods.
You post hits on an interesting aspect of US education that does not exist in many of the countries that are said to have a better educational system than the US. The states in the US with the best test scores, Massachusetts, New Hampshire, Maine, New Jersey, and Vermont scored an average of 30% better than the worst states, New Mexico, Alabama, Mississippi, Louisiana, and West Virginia. When you look at the best and worst school districts, the difference is even more startling.
In the US, only one of the top 5 states had a voucher program. 3 of the worst states had voucher systems. This accounts for much of the misunderstanding in the private vs public school battle. People that live in states with high performing public schools can't understand why people are so down on public schools in other parts of the country. People that live in the worst performing states tend to see all public schools in the US as under performing, mismanaged, and riddled with crime and discipline problems.
Which is why it should boil down to an individual choice.
You are going to find different results depending on what study you use to determine which system is better. But I think that it should be evaluated by the parents when they make their choice. I can tell you of some great public schools in our suburbs here in Cleveland, and I can point to public schools that are falling apart with a large percentage of HS dropouts. It's all a matter of what city or state you are in, what availabilities you have, and of course, resources.
School X does better in math and science than school Y. Okay, but what about on an individual basis? Are the students that opted to attend school Y doing better than they were in school X? That's the most important question.
Even if a kid goes from a D to a C average because of vouchers, isn't that worth the money to keep them and even expand them? While it may be the rest of his or her classmates in school X are doing better than his new school Y, would that be a good reason to stop him from attending if he or she is individually doing better?