Good evening and thank you for the opportunity to answer your question and for requesting me personally. Based on the information you have provided the cutting behavior as actually not that unusual. My impression is that he is probably cutting superficially and not deep enough to draw blood....or if he is it is slight.
The reason he is likely cutting is due to his having difficulty in the transition to a new environment and a new life. I realize this sounds odd but this young man was used to chaos and drama on a regular basis. Now that that is no longer present he is likely experiencing a build up of anger and frustration though is not aware of how to appropriately communicate it to you nor does he know how to channel it healthily.
The cutting behavior serves as a release of that built up tension and pressure. My impression is that he is doing this in order to not "act out" in his behaviors.
I would actually suggest that you put him back into individual therapy with someone other than yourself. He needs to be aware of boundaries and to acknowledge specific roles in his life.
I hope this helps in answering your question and that you found the suggestions to be of benefit to you and in helping this young man.
Please let me know if you have any further questions that I can help in answering for you. I want to be certain that I have answered your question completely and thoroughly.If you feel that I've answered your question to your satisfaction then I would greatly appreciate your clicking the ACCEPT button thereby giving me credit for the answer and suggestions I've provided to you. I hope this finds you well and look forward to your response.
Thank you for the additional information. Given the description he used as "it hurts inside" coupled with the start of the new school and quite possibly his feeling "out of place" my impression is that this is the reason for the cutting behavior. Encourage him to speak openly with you as a means to cope in a healthier manner. I'm also including a link to a workbook based on Dialectical Behavioral Theory concentrated on self injurious behavior that would certainly be useful with the exercises in the workbook. I think this will help. Here's the link:
Please let me know if you have any further questions before clicking the ACCEPT button as I want to be sure you're satisfied with the answer and suggestions I've provided.. Thank you again for requesting me.