Dear CMS, Hi. Is somebody on the outside telling him he sucks? What a challenge for you to try to figure out. 13 has got to be a brutal age for a kid these days, identity wise. What is normal anyway? Where do I stack up in the pile?

You being a point of stability for him could be a huge gift in and of itself. In your presence he's doing great, right on track, etc.. Lotsa reinforcement, lotsa reminders to breath. Maybe you could do a couple minutes of relaxation stretches and breathing at the beginning of each lesson. Structure it in, share with him that you're learning as you go to, willing to try new things. Make the lesson time be more than "just" a piano lesson. One person caring saved my life.