It goes back far more than 40 years. Just last week I was looking at a picture of my elementary school (built circa 1920) and even when I attended in the 60s and 70s there were gates (bars) on all the basement and 1st floor windows, and they remain there today, and the building and concrete school yard were surrounded by 8 foot fencing. When we arrived in the school yard we were to join our class and line up in alphabetical order (starting in 1st grade) in total silence.
The picture I get when I drive past the elementary school my now high school age daughter attended is VERY different. It is all on one floor and the only concrete around it is the parking lot, everything else is grass and flowers and special mulch under the playground equipment. The only fencing is between the parking lot and grassy areas on one side of the building and around the baseball field.
BTW - did I mention, I attended Catholic school and my daughter attends public school?
Which sounds more like a prison to you?
I agree, sounds pretty much the same as the schools I went to as a kid in the 70s.