When I was a kid on the playground, the bell was a signal to race to the classroom door, not because I wanted to get back to work, but because it was good to be first in line, or as close to first as possible. Some time between my student days and my teacher days, things changed. Now kids form lines at the edge of the playground and are escorted to the room by the teacher. So, now at the end of each lunch period I go out to the blacktop. I like to be on hand when the bell goes off.
Unsavory things happen when kids are bunched up without supervision more than a few seconds.
Each day we make our way back to the room as a single file line. We stop for a short break at the oasis, which is what we call the place where bathrooms and drinking fountains are. My job on the trip is to keep the line orderly. I can see the value of enforcing the etiquette of this fundamental group behavior. One need look no farther than the psychology of basic military training to appreciate its merit.