There are so many variables that you just can’t make a hard and fast rule about appropriate age.
When I taught 3rd grade in Bklyn., N. Y. most of my students (ages 8 or 9) traveled by public transportation, bus, subway, or both. A few lived close enough to walk and fewer still had a parent drive them.
But there usually was no choice or debate about the issue. If it’s a single parent home, then that parent needs to go to work so those kids learn to take bus or subway pretty early in life.
But the normal thing in large cities with kids and public transportation to and from school is that they are usually in groups small or large and traveling during the same approx. time period. Very seldom is a child traveling alone and vulnerable. And of course, they are all assiduously trained to not interact with adult strangers WHO APPROACH THEM at all. And they’re not afraid to make a scene if necessary. Plus, this is in daytime and in the city there are always other people around.
I remember this issue from years ago and Lenore Skenazy catching a lot of flack for allowing her kid to take the subway at 10 yrs. of age. They were calling her the worst parent in the world. How ridiculous ! ! As a matter of fact this was the first Q in which I participated on my first day of Fluther.
And my observation then is the same as today. For her it was a choice. How about the tons of parents for whom its a necessity rather than a choice?
This is primarily a choice for affluent people to debate about. Those with cars and plenty of spare time are available to “helicopter” their kids to their heart’s content.
For ordinary working class folks, (barely just over the poverty line) they don’t have the luxury of debate. They have jobs to go to and if they live in the city, usually no car. With parking and insurance, owning a car in the city is an expensive headache.
Both they and their kids take public transport on a daily basis because that’s how they get around. And working parents don’t usually have the type of jobs that allow for flex-time so are simply not able to helicopter over their kids. They’re too busy earning a living.
There is just no practical way to make a one size fits all policy.