First through sixth grades recess was added to burn off the energy kids have so they could calm down and pay attention.
Back in the fifties my elementary had several fenced off acres, mostly grass with a smaller asphalted area. Three teachers sort of watched over us, two for the two gates and a rover to catch injuries. Playground equipment consisted of hd steel pipe chain swings, heavy board see-saws, and steel monkey bars (try calling them that today) and several sandboxes for the youngest. Kids would split up into groups by themselves for dodge ball, tag, hop scotch, tag, or whatever. Bell would ring and we were herded to the doors, heads counted and then back to class.
Basic guiding principal was kids needed a break from teachers and vice versa while burning off energy.
The photo shows the monkey bars or jungle gym. We learned to hang upside down from our knees, hooking our feet behind the bars. Sit ups, though we didn't know it. King of the mountain tag was also played on the bars. Heaven forbid! We had some chubby kids, but no fat ones.