Most progressives I know are instinctively and emotionally against the idea of vouchers. In my case, I've long been opposed to vouchers -- for a few very specific reasons. Most of them are pretty well articulated here. All of the issues presented make sense to me, but this is the one I've been most concerned about:
A pure voucher system would only encourage economic, racial, ethnic, and religious stratification in our society. America’s success has been built on our ability to unify our diverse populations.
But I must not be too concerned about it because I took my daughter out of one of the best public school systems in the state (Chapel Hill) and put her in a Waldorf high school where there are seven kids in her entire grade. The difference has been transformative - mostly because of the approach to teaching they use, but also simply because of the small scale and intimacy.