Cubic Roots

The building is many little cement boxes pasted together to make bigger boxes. The rooms are cubes, full of little boxes known as desks. The students write on white rectangles, copying from the bigger rectangles in front of the room. They stay in their cubes, writing down only what they are told, looking for the "right" answer. The cubes are their space, where they stay until they are told to move by the teacher or the ringing of a bell. They carry their square binders and books and move to the next cube and the next and the next, following the assignments written on rectangular charts. They dare not try to move outside the box, or they will be disciplined. The boxes are everywhere.

"And this brown one was originally a box, because I feel like that's what school is, but I changed it to a book, for learning."

Why? Why is this the way it must be?