Tracy, I think Abby is totally right–maybe try sending him to a T1D teen camp! I was diagnosed at 15 and (while I did dose correctly and take care of myself) it was pretty frustrating not knowing anybody else who was going through the same thing. I have always regretted not going to a T1D summer camp and have even been looking into some T1D adult camps they do in California
Another idea is to get him on a pump if he isn’t already on one. It’s much more discreet; I use the Quick Bolus feature on my t:slim all the time so that I don’t have to actually pull out my insulin pump if I don’t feel like it. It does mean more mental calculations and ensuring you’re dosing correctly for food and BG corrections, but I absolutely love that I have the flexibility to leave my pump under my clothes and just hit a button on the outer edge to dose.
Also, I think it’s worth noting that there should be a conversation around using phrases like “things he shouldn’t have.” That makes us T1Ds feel like we’re not allowed to do or eat things that other normal, healthy people do or eat. It might help him if you talk about how he really can eat whatever he wants as long as he gives himself insulin for it. Eventually, he’ll learn that unhealthy foods aren’t good for T1Ds or non-T1Ds alike and so he’ll stop eating junk/overly sugary foods. When I was diagnosed at 15, I refused to accept that I couldn’t do anything other people could do. I just made sure that if I did eat cake or junk food or play sports, I was taking care of my diabetes properly so that I could actually do those things without long-term negative health effects.