I found an answer in some roundabout way. How to solve the puzzle:
There are 10 levers in total, 4 in classes under the pool, 1 in the pool, 4 in classes over the pool and one near the shoes. This is the levers you need to activate (left to right):
lower classes: on off off on
pool: on
upper classes: off on on off
near shoes: off
To use lever in the pool you need to drain it. Go to the room in the bottom of the screen with the pipes, then go to the storage room for the valve. To get to the storage room, go sough from the lower classes, then east.