We had a similar device (without the clear half) at the school where I attended 4 - 5 grade.
Never sure when to take you literally... at the school, as you say, or on the school building?
If the latter, how'd you get up to the top?
QUOTE
You NEVER wanted to go in a group and attract...attention
Nor did you want to be the first one out in a real emergency! Chances were great that you'd be buried by your classmates jumping in too soon and landing on top of you before you could scramble out of the way in the dust or mud (always one or the other) at the bottom!