As I teacher, I echo your frustrations. It sucks to be overworked, underpaid, underappreciated, and then blamed for everything that goes wrong in schools. However, that's the nature of the beast. Society points fingers at teachers for the same reason they point fingers at the president of the United States -- we're easy scapegoats. Now, Bush has heaped his fair share of misery upon the world, whereas teachers (generally) don't, but the analogy is still fair. Teachers are the figureheads of the classrooms they teach in. When students fail tests, fail to stand up to international competition, and reinforce the stereotype of a dumbed-down generation, who do people want to blame? Duh. It's easier to do that than to accept the fact that there are many reasons why America's students can't hold a candle to the competition. Teachers are only one head on the hydra of failed education.
But you know what? Oh well! So people don't appreciate teachers anymore. So what? We're not working for the recognition or the money. As long as they leave me enough alone to do what I do best, without fear of losing my job, they can stick their unfounded complaints on someone who cares. I know better. Out of the 120 students I see each day, if just one appreciates something I've said or done, it's proof that administration, government, and society are dead fucking WRONG. We're not there for them. We're there for our kids.
That may sound like the blissful naivete of a first-year teacher, but there's truth in it. Teaching is damn hard work. If one can't learn to find appreciation in the small things, then this is the absolute worst profession to be in.