Here's a few key points from the book listed in my local newspaper:
Student tracking finds limited learning in college
Half of students did not take a single course requiring 20 pages of writing during their prior semester, and one-third did not take a single course requiring even 40 pages of reading per week.
After four years, 36 percent of students did not demonstrate significant improvement, compared with 45 percent after two.
Students who studied alone, read and wrote more, attended more selective schools and chose traditional arts and sciences majors posted greater learning gains.
Social engagement generally does not help student performance.
Students who spent more time studying with peers showed diminishing growth. (So much for the touted benefit of "group" projects.)
Students who spent more time in the Greek system had decreased rates of learning. (Isn't that a shocker!)
Here's a link to the study that backs up their claims: What Will They Learn, A Report on General Education Requirements at 100 of the Nation’s Leading Colleges and Universities by American Council of Trustees and Alumni, 2009.