It's one of those things that you-know-it-when-you-see-it.
For example, two schools on opposite coasts are darn near impossible to flunk out of. Indeed, one of them even got rid of F-grades. In contrast, it's nearby public competitor awards D's and F's like candy, and grades science course on a C+. Or, take Brown University, with a mean senior gpa of ~3.6, which I think is the highest in the land. Of course, some college has to be at the top, but, if that ain't an example of grade inflation, what is?
but, check out gradeinflation . com