Adding a Kid to Primary Class

The primary president has generated classes. There is a 7 year old boy that she is trying to add into one of the classes but an error appears that says "Source and destination unit organization class types must match." Why is this appearing and how do I go about adding him to the class?

Assuming that you're the clerk, have you tried moving the child? What are the classes the child is being moved between? Since you say the Primary President generated the classes, have they been set up correctly?

I have the same problem with a YW list. "Source and destination unit organization class types must match." comes up when I try to add kids who are turning 12 or have turned 12 this year.