iTunesU enrolments

I am trying to see if students have enrolled and then "un-enrolled" in a course presentation I posted.

I cannot find, through web/Google searching if it is possible to "un-enrol".

I have seen (& tested) that a student can delete a course from their iTunesU app, but that when that occurs, they remain enrolled in the iTunesU Course Manager.

If student(s) is saying they have accessed/viewed/reviewed my course materials, but I cannot see them as ever having enrolled in the course (because they are not listed in Course Manager as 'Students') then is there any other way to verify they have accessed the material?

A.