Black students are more likely to attend segregated schools with high concentrations of poverty, less qualified teachers, lower expectations and a less demanding curriculum, she said.

"And they are perceived by society as terrible schools, so it is hard to get accepted into college," Wells said. "Even if you are a high-achieving kid who beats the odds, you are less likely to have access to the kinds of courses that colleges are looking for."

Students who don't graduate from high school are much more likely to go to prison, said Gary Orfield, co-director of the Civil Rights Project at UCLA. Nearly 40 percent of inmates lack a high school diploma or the equivalent, according to the census data.

"The criminal economy is one of the only alternatives in some of these places," Orfield said. "You basically have the criminalization of a whole community, particularly in some inner cities."

Blacks made up 41 percent of the nation's 2 million prison and jail inmates in 2006. Non-Hispanic whites made up 37 percent and Hispanics made up 19 percent.