Scratch-Off World Map. Scratch of a place whenever you visit it, or use this as a teaching tool. Whenever you teach the students about a place, scratch it off! This could also be used to teach students the locations of different places in the world.
This is a perfect combo of my two favorite ideas for that space under the stairs leading to the basement. A reading nook AND book storage and shelves . assuming that there is enough space for this there.