I figure it's safe to say most characters will be attending the same school, or the same two schools as sometimes there are two highschools in the same area, not to mention a junior high also. So while it'll rarely be the direct focus, if characters attend the same school, it's safe to say they'll also talk about school at some points.

It also lends to things like Culture Festival in October, test periods, and so on. I'd wager as onmyou we'll be students by day, and onmyou by night, which sounds pretty fun honestly.