Isn't that what the ESRB is here for? The idea was that the rating system is there to make sure that certain games do not end up in the hands of certain age groups. You cannot pick up an M rated game without an ID (assuming you are questionably around 18). T rated games are similar, but most of the time, they just have to be 13 and they are fine. Kids on Halo and CoD shows more about poor parenting than anything else. Unless they have people actively monitoring all of the games ever, that will never make a difference. Kids will always make a game less fun. You can just avoid them and block them. Job done.