Okay, so maybe I’m confused about that whole correlation/causation thing. But something happened in the 1960s and then again in the 1980s to cause grade inflation in colleges .
The rise in grades in the 1960s correlates with the social upheavals of the Vietnam War. It was followed by a decade period of static to falling grades. The cause of the renewal of grade inflation, which began in the 1980s and has yet to end, is subject to debate, but it is difficult to ascribe this rise in grades to increases in student achievement. Students entrance test scores have not increased (College Board, 2007), students are increasingly disengaged from their studies (Saenz et al., 2007), and the literacy of graduates has declined (Kutner et al., 2006). A likely influence is the emergence of the now common practice of requiring student-based evaluations of college teachers. Whatever the cause, colleges and universities are on average grading easier than ever before.
Commuter schools (a university where a large majority of students live off campus) and engineering schools grade the hardest while private schools inflate grades by an average of 0.1 to 0.2 higher on a 4.0 scale.
(Via: Neatorama )