School Choice?

Well I read an article by George Will the archtypical, reflective conservative and I thought about the phrase and the absurdity of it. School choice stands for, as I understand it, giving vouchers to certain parents who do not feel that the pubic schools are serving their kids so that they chose to use them for private schools. Somehow, this process will "improve" public schools by forcing them to improve or lose more students. It's truly absurd: Taking money away from public schools will somehow improve them?