Classes.
If anyone wanted to interact with anyone else outside of their team, Classes are a good way to do it. 

Here's the list of classes from 10 or so pages ago for convenience.

[hider=Classes]
>>Core Classes
Math
Science
Language
History

>>Hunter Classes
Grimmnatomy/GrimmBiology
Armory/Forge?
innawoods Survival
Dojo/FiringRange
Physical Training/Conditioning

>>Elective
Music
Pottery
Cooking
Artistry
Computery stuff
Foreign Languages?
Mechanics
Welding
Photo
Fashion
Philosophy
Religion
Psychology
[/hider]