Now, our foundation, for the last nine years, has invested in this. There's many people working on it. We've worked on small schools, we've funded scholarships, we've done things in libraries. A lot of these things had a good effect. But the more we looked at it, the more we realized that having great teachers was the very key thing. And we hooked up with some people studying how much variation is there between teachers, between, say, the top quartile — the very best — and the bottom quartile. How much variation is there within a school or between schools? And the answer is that these variations are absolutely unbelievable. A top quartile teacher will increase the performance of their class — based on test scores — by over 10 percent in a single year. What does that mean? That means that if the entire U.S., for two years, had top quartile teachers, the entire difference between us and Asia would go away. Within four years we would be blowing everyone in the world away.