My son was 5.5 when he started school and I let him walk/bike there alone. He is very, very reliable and responsible and the school was only 150m away with no roads to cross. From about 6 I let him bike to the shops 4 blocks away but we were in a very small town and he could quite easily wait until there were no cars on the roads to cross. In the city I would not let him go alone. I highly doubt I would let my DD1 do the same at that age, it really depends on the child and the town.