When parents send/let their 6 year go on own to park a mile away, that is irresponsible. And putting the supervision burden on a 10 year old sibling is equally wrong and no substitute for the parent.
I rode my bicycle to school and the park over a mile away starting at age 6 in Torrance Ca.
Oh man....I don’t want to be your child
Did your parents supervise you every hour of the day?
When I was a kid on summer vacation from school, I disappeared for the entire day riding my bike miles from my home. During school, I walked a mile or so, by myself, to my ELEMENTARY school, in all types of weather. Once we had an early release because of a snow storm. Walked home in knee deep snow by myself and enjoyed every minute of it.
When I was in the third grade, I used to go to a lake about 3 miles from my house. USUALLY with some friends. There was a canoe tied up there which was used by anyone who came. No parents hovering around. Had to be back when the street lights came on. That was in Alabama in the 60s.
Different environments make for different decisions, I'm sure, but You may be aghast, and I don't blame you if you've always live in particularly dicey neighborhoods. But parents can judge their own neighborhoods and the competence of their own children.
I raised my own boys similarly.