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.
I remember a teacher once explained to the class schools and prisons share several design features.
They're durable withiut sharp edges, so destructive morons can do little damage to the buildings ir themselves, they use those flickering white lights that drain the energy from you, and they're designed to hold mass amounts of people who dont want to be there, supervised by a much smaller amount of people.