HQ Abandoned School - it's a completely modular flexible set of 3D-models, textures, materials, and shaders that will let you dive into an atmospheric abandoned place of the previous century. 

For this moment this pack includes 7 pre-made rooms in the demo scene interior (two classrooms, two toilets, library, gym, lockers room, and corridors).

You can enter into the interiors from the outside.

Without numerous words - just watch the VIDEO and look at the screenshots.