There is now increasing evidence that students who receive large preferences of any kind—whether based on race, athletic ability, alumni connections or other considerations—experience some clear negative effects: Students end up with poor grades (usually in the bottom fifth of their class), lower graduation rates, extremely high attrition rates from science and engineering majors, substantial self-segregation on campus, lower self-esteem and far greater difficulty passing licensing tests (such as bar exams for lawyers).
The most encouraging part of this research is the parallel finding that these same students have dramatically better outcomes if they go to schools where their level of academic preparation is much closer to that of the median student. That is, black and Hispanic students—as well as the smaller numbers of preferentially admitted athletes and children of donors—excel when they avoid the problem of what has come to be called "mismatch."
-from today's WSJ and its Saturday Essay by Richard Sander and Stuart Taylor, Jr., entitled "The Unraveling of Affirmative Action".
Those authors have just published Mismatch: How Affirmative Action Hurts Students It's Intended to Help, and Why Universities Won't Admit It.