Teresa's note says homeroom 62-A, which probably got subdivided along with the dorm rooms, if the name is any indication. She visits the bathroom with a Seoul girl in her hall and has a superficial conversation in Mandarin on the way to the top floor; from there the corridors are crowded enough she doesn't need a buddy.

The room itself is crowded, three large tables with chairs and desks crammed in between them with inches between them. The walls seem crowded, too, there are a lot more lamps than necessary to light it. This matches the 'subdivided' theory, possibly? 

She's not first, but no one she'd previously noted is here yet. She grabs a pointer resting against a wall and tests a few desks, then takes one that lets her keep her back protected and watch others come in.