I think the question you have to ask yourself is that if the behaviour has negative effects in other areas of his life? Does he interact w/ others meaningful? Is he engaged with what he is learning? Is he able to discuss what he is learning. I think some kids just enjoy learning on their own and computer courses give them that feeling that they are doing it on their own. I would break it up during the day as to minimize eye strain. And of course this varies depending on the age. I know a kid, older than yours (10yrs old) who did all his course work online (EPGY Math, EPGY Science, EPGY Language Arts).
Dazey
