http://articles.latimes.com/1997/jul/16/local/me-13288
http://web.archive.org/web/20000829094953/http://www.pcmagic.net/abe/gradeadj.htm
According to that Los Angeles Times article from 1997, the colleges’ GPAs were rated in comparison to LSAT scores (not grades of enrolled students in law school). Not exactly a big surprise that more selective schools (where students needed to be good test takers to get admitted in the first place) did well.