There is a way to block student access, without expelling them from the course. This allows you to restore their access once any discrepancies or backlogged payments are settled.
Click Students on the side bar
Locate the student's name (you can use the search students function) and click edit
3. Scroll to the bottom of the edit student page and click lock this student accessing the system.
4. Click update student.
5. When you are ready to allow the student access again, repeat the above steps, undoing the lock button.