Cater comments on how classwork seems so effortless for Leona, with Leona explaining he learned everything they teach at NRC from private tutors at an early age, “with a curriculum way more advanced than I’d have had in school….I don’t know what I know ’cause I’m always hittin’ the books like your housewarden. I just already know it.”
Idia explains, “Leona’s still royalty. Totally makes sense he’d have top-notch magic instruction as a kid.”
Leona being objectively more intelligent than most seems to be well known by the other characters: Vil says, “As loath as I am to admit it, (Leona) wasn’t wrong when he said he was smarter than the rest of us,” and Cater’s cover story for bringing Leona into the Heartslabyul of Trey’s dream is wanting to receive tutoring “from the big brains,” also saying Leona is “so smart.”
It is possibly for this reason that Leona so rarely attends class (though he says that he does show up for test days), saying that classes “are the most boring thing in the world” for him because there is no point in doing things you already know you’re capable of.
Leona says his favorite subject is ancient incantations (“It doesn’t bore me like all the other ones”), a class about deciphering dead languages. Leona explains,
A lot of them were created to conceal magical rites, so they’re over-complicated on purpose. Even experts in the field have their work cut out for ’em. Making out individual characters is hard enough, let alone grasping the meaning of whole words or enough grammar to understand sentences. You just gotta keep inching forward, analyzing what’s there and comparing it to what’s already been deciphered, looking for similarities.”
(A lot of work for the favorite class of a character who is infamous for his dislike of putting in effort, Vil claims that Leona only gives an honest effort with things that make his life easier, but this also seems to apply to tasks that challenge him, such as when he stays up all night deciphering a history book on ancient food preservation methods on his birthday, for fun.)
Leona is possibly also adept at animal linguistics, eavesdropping on a conversation between Ruggie and Lucius and complimenting Ruggie’s fluency.
Twisted Wonderland Reference Note 