The good news is that the American public is finally becoming aware of how tenure and other union-enforced policies make it nearly impossible to fire even the worst teachers. This article from L.A.: Dance of the LA Lemons has examples that will make your blood boil.
And, of course, when school systems can't fire bad teachers, they often transfer them to inner-city schools where parents have less power and voice (or knowledge) to do anything about it, adding greatly to the cycles of illiteracy, under-education and poverty that keep families trapped. Hopefully by getting more of these examples out to the public, something will be done about it.
But the bad news is that, while the American Federation of Teachers, for example, is declaring new support for making it easier to fire bad teachers (see AFT speech) , their actions show they will do anything but. Sources tell me that AFT President Randi Weingarten is personally holding up the DC teachers' union contract, which would make it easier to fire terrible teachers (and which would have paid great teachers more...but the union nipped that concept in the bud immediately). There's more (stay tuned). But just because the unions see a public backlash coming and are saying what the public wants to hear, don't for a second think they will relinquish anything that reduces their power if they can avoid it. We'll all have to wait and watch.