That doesn't say its "normal" by 6-7. It just says that some kids are able to do it as young as that age. And the specific child in the article didn't start unt

That doesn't say its "normal" by 6-7. It just says that some kids are able to do it as young as that age. And the specific child in the article didn't start until 9. Plus, I would argue that there is a difference between sending a kid off to school at a given time and leaving them home alone with a specific schedule of "At 8:45 you need to walk to the bus stop and wait for the bus". Which again, I'm not sure I would trust to my 5 year old to do on her own every morning. Not because she can't walk alone, but because I don't think punctuality is something she's mastered yet. And even the article admits that young kids can do that more because of "social trust than self-reliance". And I don't know how many parents are willing to rely on other adults to help out their kid if something goes wrong.