To delete a single class from your calendar go to -
Select the class on the calendar, then select Roll Call to get to the Roll Call page, then select the 'Delete this class' button. This will delete that single class instance.
To delete a series (multiple) classes from your calendar.
(Example if you wish to delete all classes after a certain date)
Go to Dashboard -> Manage Classes, and find the class and select the 'View' icon. Doing this will show all the classes by date.
Select all the classes after the last date you want the class to appear and then select the 'Delete Selected' button.
I hope this helps. Let us know if there are questions on these instructions. We love helping.