It goes to reason that colleges with the most resources have the highest graduation rates, but they often do a poor job of admitting low-income students who could benefit the most from their services. The schools that do take in a high number of students without means are often bereft of the resources to help them complete.
https://www.washingtonpost.com/news/grade-point/wp/2016/09/22/ipartisan-senate-bill-takes-a-carrot-and-stick-approach-to-boosting-college-access-graduation-rates/ The Washington Post