I'm not sure about an Academy arc. I've written something where the first couple Volumes are focused on the MC attending an Academy, and later she returns as an instructor, but I wouldn't call any of them an Academy 'arc'.
When I think of an 'arc', I'm thinking of a story arc, a sub-story within a larger whole. Having a 'training arc' makes sense, and calling it an 'Academy arc' I guess would fit, but the trouble is that training is usually pretty repetitive. Which means you'll want, as others have said, to focus on what the MC is doing at the Academy, why they're there, and the moments of their training where things come together, where they learn new details that change the paradigm in some way.
Do not, except maybe as a one-line 'class was normal today' setup / filler line, go into any kind of detail on each and every nigh identical day.
Just my 2c.