You can view your class roster and active activity sessions by opening the classroom window on GMA. You can also change the status of a session (active/joinable or inactive/un-joinable). This feature is great for closing sessions when a deadline has passed.
Navigate to your classes by clicking on the “Classes” tab located on the left-hand side menu. Then select the class you would like to view.
You can view the activities that have been assigned to that class and their status on the right side of the page. If an activity is open, the box under “Allow Join” will be checked. If you want to close an activity and make it un-joinable, make sure that the box is unchecked.