When I was in elementary school, this stoplight hung in the cafeteria/gym. It was used to control the volume of voices during lunchtime.

A green light symbolized free talk. Students could talk as much as they wanted.

If the yellow light came on it meant students were getting too loud and needed to whisper.

Once the red light came on, children quickly hushed what they were saying. You could hear a pin drop. If anyone spoke while the red light was illuminated, they were banned to “the bad table” to sit alone during the rest of the lunch period and quite possibly the rest of the week.

I think a stoplight would be great for any school. It beats a loud whistle.