Proficiency is a semi-hidden stat in Adventure High.
It's visible from the menu and shows how proficient a character is in a certain type of magic.
Generally, high tier spells gives more Proficiency compared to a low tier spell.
So, for example, the Protagonist's Suppression spell gives one Proficiency point, while Confuse gives five.
If a character is lacking a certain type of spell naturally, she or he must attend a Secret Notes class in order to unlock that type of spell.
Characters who already has that type of spell unlocked may still attend the class, thus getting a boost in their Proficiency with that type, making it easier to obtain new spells in that tree.