Oh man. Back in the 70s we used to ride our "dirt bikes" and pop wheelies all over the playground. And occasionally after school we'd set up ramps (progessively further apart) and try to emulate Evel Knievel.
Today that would spell expulsion, no doubt.
Interestingly, I live near several "inner cities" and when I drive through those neighborhoods I think it's 1955 all over again. The kids play in the street without helmuts, use hardwood baseball bats in their games and there's never an adult in sight.