The problem is that most teachers are not particularly skilled. A lot of curricula are not that good.
So, really the question is something like "are you one of the best 1000 teachers in North America?"
If not, you're gone in 10 years, and that's a good thing (for students).
EDIT> I've been thinking about this a lot recently. It's a huge problem for society. Software is leverage. We don't need as many people working, but we still structure our society so that people need to work. More and more technology means that if you're not one of the best in your field you don't matter. So, how do you eat?