While in your planbook, click the menu at the top right of any lesson in the class you want to change.
Then, click “Edit Class Setttings” at the bottom of the menu. Click "Delete Classes" and then click "Delete It" in the pop up.
Note: Once you delete a class, all lesson plans associated with that class will also be deleted. If you accidentally delete a class, email email@example.com. In your email, make sure to include the 1) class name, 2) planbook name, and the 3) the first day of lesson plans for that class.