The concept is cool but I think the flooring and depth isn’t that great.

For the pool background try and implement these features / follow this:
-Make the water non-existent and instead create the floor of the pool and it’s walls with blue gradients etc. to make it seem like there is water and you can see through it.
-Add Pool noodles and other swimming pool equipment
-Add paths to changing rooms
-Add some lights on the roof
-Put the chairs and things further back and give the pool depth by making it all in a trapezoid shape like how you would with a road going off into the distance.

As for the classroom:

-Add desks
-Add chairs
-Add an openable door
-Add whiteboard and maybe an interactive board
-Add teachers desk
-Maybe Add some pencil cased etc,
-Finally add depth, not much though because it’s a small space but still aim to add some.

Sorry for the repetition and the lengthy comment but hopefully it was of some help to you.