User groups in conjunction with buildings allow administrative users to assign granular permissions to students in specific groups. A list of all active groups in your district may be found by visiting Settings (left menu) > User Groups. Creating user groups:
Allows users specific access by default to all/specific documents
Limit users access by building
Locks down permissions of groups
An administrative user or owner of a document can only change permissions for a collaborator based on the parameters of their user group(s). That is, their default and max permissions. For example, when adding a collaborator Minnie (the owner of the document) cannot give a user who is a member of user group "WHS-GenEd-Teachers" Is Owner access if the user group Max permission has been set to Can Edit. The user group will either need updated permissions (eg. that form or globally, the group would need a Max permission of Is Owner) or the user will have to be removed from the group.