My school irl was just a big building made from pebble-concrete in Germany-typical grey, but in my dreams it always was this old overgrown weathered temple ruins with long shadows and late afternoon sunlight, like something out of Shadow of the Colossus, sorta like this
And the indoor-areas were always dust covered abandoned swimming pools with syringes and stuff lying around, Pripyat-style, like this:
The outdoor-areas were always really peaceful and idyllic and there was no people around, but the indoor areas were unspeakably horrible. There was an animated dried corpse dwelling there that everyone just called "The Serbian" who would try to hunt me down whilst dragging himself over the tiled bathroom floors.
School, eh.