Throughout much of 2011, we heard about the widening income gap between average Americans and the wealthy. Frustration over income disparity helped to fuel the Occupy Wall Street movement.

But the income gap may have deeper roots than anyone imagined. And its impact on American society 15 to 20 years from now is going to be dramatic.

Educators have focused considerable attention since the 1960's on closing the achievement gap between black and white students. And some progress has been made in closing the black-white student achievement gap. But the achievement gap between rich and poor students has grown by about 40 percent during that same time, according to studies recently reported by the New York Times.

"We have moved from a society in the 1950's and 1960's, in which race was more consequential than family income, to one today in which family income appears more determinative of educational success than race," says Sean Reardon, the Stanford University sociologist who authored one of the studies.

A University of Michigan study found that the disparity between rich and poor students in college completion has also grown by a sharp 50 percent since the 1980's.

Both studies were completed before 2008 and don't reflect the impact of the recession, which probably widened the gap even more, the researchers say.

The explanations for the gap are not surprising. Wealthy parents, the Times article says, are able to spend more time with their children and devote more of their resources on their education. The researchers refer to it as "cultivation."

But there is also a multiplier at work that compounds the problem, since studies show that educated people tend to marry other educated people. And those couples are likely to form a two-income household of higher earners, says the Times, while less educated Americans are often single parents.

Instead of education leading to increased opportunity for most Americans, the researchers say we have a formula in place that narrows it. And the long-term consequences are serious.

How will the US compete in a global business environment with a large undereducated workforce? How do we narrow the achievement gap and increase upward mobility at a time when funding for education and job training is shrinking?