Why not give him his own laptop and leave him to it. Forbidden fruit ALWAYS tastes sweeter. Once he has his own kit and internet connection he'll leave yours alone. It is perfectly possible to stop him viewing porn sites if that is the fear. Most other stuff he can access at school anyway. We can prevent his accessing here because we will spot his ISP, which will be the same as yours if you set him up on an intranet at home, AND stop creating multiple identities for yourself.