depends. my kids school in china didn't allow me to let my kids bike to school without supervision. (well, actually, they couldn't stop me from sending them to school alone, but they would not let them out unless i was there to pick them up. (there was only one crossing on the route, and that was close to the school and didn't have a lot of traffic)

in germany on the other hand, there was a case where parents demanded a school bus for a 7yr old, but the court said the kids could take the public train to school on their own.