Dries Buytaert maintains a list of education sites using Drupal; definitely worth looking through, especially if you're in the process of selecting an official CMS for your school and need some good in-the-wild examples.

Not sure how comprehensive this is, but it looks to be a very helpful list of educational institutions currently using Drupal. Also, it's a wiki page, so if your institution isn't listed, you can add it!

Jeff Robbins talks to Bill Fitzgerald of FunnyMonkey about how Drupal is being used in universities, high schools, and other educational institutions.

Final Report on UT's CMS Selection - pdf report detailing UT's selection process, and why they eventually went with Drupal.