If you have achievement profiles, you wish to remove from a class you can do so by doing the following

School setup> marks and comments> assign achievement profiles to classes> go 

The following screen will load with the classes and current assignments, click on the second option at the top of the screen " Assign by class" 

remove the check mark in Only apply to classes without achievement profiles and select profile to assign to Remove profile. 

 You can remove all or choose the class you want to remove> assign (bottom right corner of screen) 

Task will be sent to the notification bell> close the screen> profiles will be removed.