As the Teacher of the class, you can control who can be in your class by adding the members or removing 

• Click All Groups at the top left corner
• The left navigation tray opens up 
• Click the name of the class
• Select Staff
• Click to expand the Invited section
• Click on the name of the member who needs to be removed from the class
• Click Options in the top right corner of the profile screen of that member
• Click Remove from Class
• Successfully Removed User pop-up will be seen
• Click Confirm.

Note: The invited member is removed from the class. The updates/events posted to the class will no longer be sent to this user.