You can use your CDSA Workspace Accounts for as long as you are a student of CDSA. As such, each year, you may need to unenroll your subjects of the previous year (unless your teacher has unenrolled you first). Here are the steps on how to unenroll your previous year's classes/subjects.
1. Login to Google Classroom using your CDSA Workspace Accounts.
2. In the Classroom page, you will see all your enrolled subjects, even those from previous years. To unenroll, click on the Menu button (three vertical dots) on the upper right of each class card. Then on the pop-up choices, click "Unenroll".
3. Just make sure that the classes/subjects you are to unenroll are from the previous years. If you have mistakenly unenrolled your current classes/subjects, just add them using the Subject Code or Classroom Link provided to you by your adviser.
For Mobile devices, the procedure is the same. Open your Google Classroom App (make sure it is logged in using your CDSA Workspace Account), and follow the steps above. See image below.