Hi there,
I've been doing some work supporting classes that use Omeka, and in order to better serve them, I've made a plugin called "CourseTools" that adds two roles to Omeka, "students" and "reviewers".
Reviewers are basically just researchers with expanded read access to the site, because I noticed that they don't have access to non-public Exhibits.
Students, however, are a bit more interesting. I have them set up with customizable permissions, so that Super Users can change what students have access to on the fly.
I've only just gotten it to a point where I'm pretty sure it works consistently for a pretty simple installation that includes Exhibit Builder and Neatline, but I'll be testing it with more plugins and making sure it holds up (especially now that I'll have a few instructors using it). I've put it out under a GPLv3, so if anyone wants to use it, or just take a look, it's up on GitHub here:
https://github.com/jaguillette/omeka-plugin-CourseTools
-Jeremy