We are inner-city suburbs and a lot of kids walk to school alone or with friends from Grade 4 - kids younger than that are sometimes with older siblings. DD1 wants to as well but I have said Grade 4 is the minimum so she will be 9. Apparently the spatial awareness isn't fully developed in their eyesight until after 8yo so they can't tell how much distance they have between them and a travelling car until that is developed so that's why 10 is recommended from my understanding.