Greek life and grades

My son is about to transfer to a big state university and will probably be going through rush to join a fraternity. He is very socially oriented, people seem to like him and I have no doubt that there will be fraternities that want him to join. My main concern is the effect that being a member of a fraternity will have on his grades, his ability to study, and his academic focus. I would like to hear from anyone with experience of the effect of greek life on academics.