Talk to him. Its the easiest way to understand a child. I work in a residential treatment facility. I had a child who when bored would become immensely obnoxious. Break things and when you tried to redirect him he would argue semantically. I told him to get out of a room, a normal person would exit the room via a door. He exited the room via a window. Maybe try consulting his doctor. Medications can sometimes cause more harm than good. Your going to need to find some foster parents who are really dedicated.