What are the laws for moving out 4 months before graduation?

I live in pennsylvania, and my boyfriend (christopher) has gone to cys (children and youth services) and the police about his parents abuse. His dad has hit him and has admited to the police and cys that he has hit chris. They sent chris to live with his grandma for the weekend because cys is closed on weekends. Monday morning they called his mother and told her she can pick chris up because the investigation was closed. We believe that his dad pulled a connection because he’s a correctional officer and that’s how the case was closed to quick. But the physical abuse has now turned into mental abuse. He just called me to tell me his mother found his sisters cigarettes in his room and she made him put his hands flat on the dining room table and everytime she asked him “where did you get them” and he said “I dont know” she smacked his hands with wooden spoons. They call chris stupid and laugh at him because he struggles with math. He is enlisted in the army to leave july 27th, 2010. I talked to a friend of my mom’s who works for cys and she said that because chris is 17, enlisted in the army and graduating this coming june that he does not have to live at home. He can move out as long as he has a place to live. And that he cant be listed as a runaway because his parents know about his where abouts. But his case worker told him he can not leave until he is 18. But I think she is lying for his step dad because of the whole connection thing. If he leaves, can his parents do anything about it since it is 6 months from his 18th (july 17th) birthday and we’re graduating june 4th ? If he leaves what could his parents do to him ?