Hi - this topic has come up before, and there are a bunch of replies here, including a link to state laws on the matter: http://giftedissues.davidsongifted.org/BB/ubbthreads.php/topics/94568/1.html

For me, I've occasionally left DS8 alone, with a phone, for an hour or two since he was 7. Totally depends on the kid, the family, the laws of your state.