While Sable practices walls, Neo sketches out a design for the tower and what goes where. A bit of math about dorms and common rooms and the minimum wall thickness for the magical reinforcement spell (half a meter) gets her a tower diameter of twenty and a half meters, including a central spiral staircase. The ground floor gets to be entirely taken up by the infirmary. An animal processing shed goes in a wooden outbuilding against the outer wall. Next floor up is seven training rooms, one per element, with a study area in the center full of desks and tables. Then seven apprenticing rooms, again one per element. These two are the closest rooms to the infirmary because they're the most likely in-tower buildings to produce injuries, so they should have the shortest trip. That's also why the infirmary is on the ground floor, to allow injured hunters or defenders from outside the tower to be brought in quickly. The next floor above the training floors is the kitchen and dining room, with lots of round wooden tables and comfy chairs.
Then above that go five floors of dorms, just to future-proof. Every dorm floor has twelve dorm rooms and two bathrooms, evenly divided radially, each room four meters long. Each dorm gets a bed, a window, curtains, a wardrobe, a desk, a chair, and some bookshelves over the desk. The central area of each dorm floor has a common lounge, full of comfy couches and chairs, tables, and more bookshelves. All the bookshelves get filled with blank notebooks to start, and stacks of looseleaf, binders, and pens and pencils. They've handled enough of all of those to conjure them freely. Above that goes a crafting floor, then a research office and lab rooms. The crafting floor only has the wand shaper for now, the research office gets the research desk the previous Magisters talked about, and the labs have tables and open spaces and bookshelves of notebooks and such.
Finally, the top two floors are special. The second-highest floor is the Headmistress's suite, reserved just for the five of them, and optionally anyone else who joins their little polycule. There's a very small landing area where the stairs reach the floor, but otherwise it's completely walled off. It features a cozy lounge, a private office and workshop, a deeply luxurious bathroom with an enormous bathtub, two smaller bedrooms in case someone needs their own space, and a fucking huge master bedroom. The bed there is wider than an Alaskan King, wide enough to make this bedroom the largest room on the floor, because the five of them refuse to ever sleep alone again. They have each other to cuddle now.
The highest floor is the auditorium, because there doesn't need to be a staircase obstructing the center of the room. The center is then reserved for the central stage (with just a little hatch to enter through), and gradually raised seating radiates outward from that.