College Park's rating of D is based on the fact that undergraduates are required to take courses in only two of seven subject areas: composition and science.
It's not clear to me that these ratings will persist beyond the current year, since this is said to be the third year the survey was carried out and I don't see evidence of previous results.
I'd like to know how graduation rates correspond to the curriculum rankings.
In fairness, this rating seems to be based only on what general education requirements each college has. No one is measuring
- quality of undergraduate programs as they are actually run
- level of responsibility shown by post-tenure faculty
- supportiveness of work environment
- quality of intellectual environment
- average level of internal funding for programs without external support
- administrator-faculty ratio
- proportion of adjuncts and TAs in the classroom, etc.
Whether Maryland would get a D or some other grade if these things were examined is not something the site addresses. I'm too bashful to offer my own opinion.
Some current Maryland people are reacting to the ranking, though: http://terrapinsanity.com/2011/08/31/d-is-for-devastating/