Teachers' Unions are, I think, far and away the most overdiscussed element of K-12 education policy. What bothers people legitimately about teachers' unions is that taxpayers have an interest in getting a good value for our K-12 school dollar, but providers of K-12 educational services have an interest in evading accountability for results. But as Stephanie Saul writes for the New York Times what happens when you go 180 degrees in the other direction and have for-profit online charter schools is that it turns out that providers of K-12 educational services have an interest in evading accountability for results.
The actual policy issue ought to be the same across both domains -- people who want to get paid money to teach kids in school should only do so if they're actually doing a good job. But in conventional political terms you'll see these two issues line up like they're totally different. The people who demand tough accountability from traditional public schools will often be cheerleaders for shady for-profit enterprises, and the people most indignant about shady for-profit enterprises will be the first to make excuses for poorly performing traditional public schools. Ultimately, though, what matters is not the underlying organizational structure of the service provider but whether or not the system is set up so that resources and students flow toward effective providers and away from ineffective ones. If we end up privatizing K-12 education only in order to replicate (or even intensify in the name of "flexibility") the same results-don't-matter attitude that reformers complain about, it'll be the tragedy of the century.