Rich and poor students don’t merely enroll in college at different rates; they also complete it at different rates. The graduation gap is even wider than the enrollment gap.

In 2002, researchers with the National Center for Education Statistics started tracking a cohort of 15,000 high school sophomores. The project, called the Education Longitudinal Study, recorded information about the students’ academic achievement, college entry, work history and college graduation. A recent publication examines the completed education of these young people, who are now in their late 20s.

The study divided students into four equally sized groups, or quartiles, depending on their parents’ education, income and occupation. The students in the lowest quartile had parents with the lowest income and education, more likely to work in unskilled jobs. Those in the highest quartile had parents with the highest income and education, those more likely to be professionals or managers.

In both groups, most of the teenagers had high hopes for college. Over all, more than 70 percent of sophomores planned to earn a bachelor’s degree. In the top quartile, 87 percent expected to get at least a bachelor’s, with 24 percent aiming for an advanced degree.