Q. Is it a problem that the U.S. doesn't have a formal system?
A. It's a huge problem. More than 70 percent of children start "school" in some way, shape, or form by age 3 or 4, meaning they are in a program that's intended to help prepare them for kindergarten. But these kids have such widely different experiences in their preschool years that when they enter our formal education system, the levels of readiness vary enormously. That makes it very difficult to have an early-elementary-school curriculum that's appropriate for all kids. When children enter "real" school, teachers end up having to meet the needs of those who can't even recognize their letters and numbers, as well as students who are already reading and doing basic math. And beyond that, I personally believe that every child deserves a high-quality preschool program -- no matter where he lives or how much his family can afford to pay.