This is what/who I used to draw more than twenty years ago (my god, I can actually say that I was doing something significant 20 years ago!!!) But yes, this was what we looked like back then. I went to a Catholic school run by the Benedictine order, originally by German nuns.
The uniform is of European roots (think “The Sound Of Music”). If you’re wondering why lunch is on the floor, it’s because many of us really did sit in groups on the ground to eat (even if there is a seat available).
Now, the magical pocket of possibilities is a “secret” pocket. It is sewn into the skirt and blends in with the rest of the stitching and the pleats.
One may not initially know that it exists but I think it has the same powers as Hermione’s bag!