Any teacher on the school account can move a premium class subscription from one class to another.
How to move a premium class subscription
Click 'settings' at the top of your Teacher Dashboard
Click 'manage' in the Manage Students box
All classes with a premium subscription will have a gold star on the right. Click 'view details' underneath the star for the class you want to move the subscription from.
Click 'move this to a different class'
Select the class you want to move the subscription to in the dropdown menu then click 'move'