The High School I went to in the 70s was quite large and had an open campus. Completely open to all grades. You'd get detention for cutting class, but the school itself was open and you could come and go as you pleased. (This was in a city in NY, about 90 miles from NYC.)

The High School my kids went to was closed. The rules were you could not leave, but the doors themselves were not locked. Years later my kids confessed to me that they frequently snuck away, especially for lunch.

"Hold on, my friends, to the Constitution and to the Republic for which it stands. Miracles do not cluster and what has happened once in 6,000 years, may not happen again. Hold on to the Constitution" - Daniel Webster