Society Of The White Horse
Probably the most private of the Schola societies, they have a sister group based at Snap.
They are focused on agricultural land magics, horses, and a certain amount of liminal psychopomp work (which they keep particularly quiet.)
The Magic of Four discusses people invited to the Society of the White Horse during the 1946-1947 school year.
Grwn from Goblin Fruit is a member, as are others in his family.