Who is your line manager? Can you speak to him with that person? If he is refusing to obey your instructions, I would start commenting to him that he appears not to be coping in a mainstream school. Tell his parents that, too. There is a pretty serious health and safety risk if he insists on walking away from you every time you talk to him. On a longer-term note, I would find out more about him and what he is interested in and try to engage him and create a relationship with him. I expect you (unwittingly) give off rays of irritation/annoyance/possibly fear or uncertainty with him, and this is not conducive to him responding to you. Get him when he is least expecting it. Ask for him to be sent to your office, or room. Create behaviour agreements that you can refer to. Show him how you work with other members of staff. When the staff he does respond to are telling him off about something, stand near them in support, and add in your two penneth. And don't worry - we've all been there with Nightmare Child. The fact that he obviously responds well to other staff is annoying, but try to think of it as him making you into a better teacher. If they were all angels we'd never have to improve!