What a splendid story. All the characters are absolutely spot-on. I can so easily see Minerva being the kind of kid who got along better with her teachers than with her peers. Then you've got Albus, displaying all the qualities that make him who he is, for better and for worse -- there's no whitewashing. And Horace is such a scene-stealer, I love it.
I also have to note how good the structure and pacing are. Stories of this length can often feel either draggy (like it should have been a short story but got out of hand) or rushed (like it should have been a novel but the author ran out of time). But this one really hits that novella sweet spot. Excellent work.