When I started school (age 6) from day 1 I walked to school and back by myself. The school was only a few blocks away but I still doubt that'd fly today. I remember basically ever only eating and sleeping at home, the rest of the time it was playing outside with friends. There was no abandoned building, basement, cliff, railroad track, cave or whatever we didn't explore, no tree or roof we didn't climb. Somehow, to my knowledge, no one ever got seriously hurt but obviously bumps and bruises were a daily occurrence.

Our parents were largely ignorant of the risks, but that just made them approach them more realistically by accident.