Google evaluates web pages on edu sites like every other web page. However their real PR (completely different than toolbar PR) is given an extra weighting. No one can tell you what this weighting is. It might make these pages twice as valuable or 100 times more valuable.
I guess my question would be, have you setup controlled experiments that show this conclusively? I deal with EDU domains all the time and found that they seem to offer a better effect in terms of rankings, but since no one can view internal page rank calculations, how are you sure they do not offer a benefit more than the average link?