I don't think there is a legal age, and i think each child is differnet anyway. I wouldn't leave my boys at home alone at all until i felt they where mature enough and responsible enough to leave unattended, even if it was for half an hour...i guess each child is different though so for example if my eldest child was 13 and i left him at home wouldnt mean i would leave my younger child at home when he was 13 unless i had the confidence that he is mature enough to be left...ykwim?