Users that don't have the viewhidden permission are able to see other hidden users in the Roster.
If student A sets there privacy to hidden, student B can still see them in the roster list view.
Steps to reproduce:
-Log in as a student
-In My Workspace view, go the preferences
-Go to privacy status
-Either choose to hide in a specific site then click "Update", or click "Hide Me in All Sites"
-Log in as a different student
-Go to the site that you chose to be hidden from as previous student (or any site if you chose to hide in all sites)
-Go to the Roster tool
-Student that is hidden is visible in the Roster