Hello and Thank You for using Just Answer.. Your girlfriend's son is in the teenage years in which children will test parents' limits and tolerance levels. Your girlfriend needs to make it known what is expected of him and what the consequences will be for not following the rules. Take away the tv, the computer, the cell phone, and the video games. Do not allow him to spend time with friends. Make him stay at home in his room and make it feel like jail. That should send a strong enough message to make him quickly get his act together and realize who REALLY is in control.