Has he figured out how to clear his history and cache? Does he use a browser with a privacy setting? Kids are pretty smart these days abut that stuff. You may want to make sure the history is set for many days and monitor that.
My router allows me to control when internet access is allowed so I can make sure that the kids aren't on late at night or when they have things they are supposed to be doing.
My router allows me to control when internet access is allowed so I can make sure that the kids aren't on late at night or when they have things they are supposed to be doing.