Batchelor Middle School in Bloomington, Indiana, USA.
Ironically, there were very few walls inside. Classrooms were separated by accordion dividers which could be pulled back to connect three classrooms into one big classroom. There were no back walls to these classrooms, just a huge opening at the back. I'm told that's been changed in a renovation.
Wow, that made me go and lookup my old middle school. It's pretty similar, a no windows, all brick building in N. Texas. IIRC quite a few of the classrooms had movable walls, I guess to adjust for class sizes/subjects. It was all flourescent lighting and recycled moldy air. I think I had a runny nose and itchy eyes all through middle and high school due to allergies