They glide elegantly along the threads with their skates, but they have no will of their own. The witch is merely controlling them with her threads.
For the witch, whose gaze was always cast down at her feet, her classmates may as well have been pairs of disembodied legs. The blouses from her minions’ uniforms are therefore unneeded, so they’re hung up to dry throughout the barrier.
The barrier of the witch– who was always looking at the sky outside– may seem too wide and barren to be a classroom, but since her minions are wearing indoor shoes, it seems to still technically count as one.
Although they glide gracefully on ice skates, these familiars are just mindless puppets on wires being manipulated by their Witch. When the Witch was still a girl she always hung her head in shame, so it is enough for her if her classmates have legs. Since they don't need school uniform shirts, their unneeded tops hang on clotheslines throughout the Labyrinth. Since as a girl the Witch was always looking out the window in class, the classrooms in her Labyrinth are minimalistic to an extreme, but judging from the indoor shoes that her Familiars wear, it is indeed indoors.