PSFS Religious Ed - Quick Start: Why is Unknown Grade associated with my classes?

The legacy Religious Education module data is migrated to the Religious Ed Design module, which may have an Unknown Grade associated with the class. Edit the class to un-associate Unknown Grade.

How to edit a class and un-associate Unknown Grade

Select Classes & Sessions from the Navigation Bar > Select Classes tab.
Use the filters at the top to narrow down the class list if necessary. Click Apply:
Select the class name under the Name column:
The class details window displays. Select the Edit (pencil) icon at the top:
Use the drop-down for Grades and uncheck Unknown. Modify the grades selected if necessary:
Select Save in the bottom right.
Repeat for any classes with Unknown associated where Unknown is not needed.