Atlanta's a good example of a city that's quite sprawling, where there's a sharp division between where blacks and whites live, between where low-income and high-income families live.

We don’t really care about test scores. We care about adult outcomes.

There's an evidence from a number of studies which show that where you grow up and the age at which you move to the suburbs or to a neighborhood that in general seems to have better conditions can really affect a child's outcomes. The kids who moved at young ages are dramatically better as adults. They're earning 30 percent more, they're 27 percent more likely to go to college, relative to the kids who stayed in the high poverty public housing projects. And so there's clear scientific evidence that you can change kids' outcomes just based on where they grow up.

Every extra year you spend in a better environment makes you more likely to go to college, less likely to have a teenage pregnancy, makes you earn more as an adult, makes you more likely to have a stable family situation, be married, for instance, when you're an adult.

Cities that tend of have better schools for middle-income families, they tend to have much better prospects for kids moving up in the income distribution.

The latest research on social mobility showed that there's a large aggregate decline in the U.S. in your chances of earning more than your parents. But I think where the story becomes more optimistic one is that there are pockets of America, where children from low-income families have significant chances of rising up in the income distribution. This finding of big geographic variation is an encouraging one because it shows that there are places where we see the American Dream thriving and we simply need to understand how can we replicate those successes elsewhere throughout the country.

Atlanta's a good example of a city that's quite sprawling, where there's a sharp division between where blacks and whites live, between where low-income and high-income families live.