I reconnected today with an old friend who also has a child with diabetes. Her son is a pre-teen undergoing the hormonal craziness of puberty.
I recall our diabetes educator recounting stories of blood sugar challenges with teenagers. For one thing, there's the issue of fluctuating insulin needs coupled with daily hormonal imbalances. The second (and probably more important) is the "teenage brain tumor" associated with the "know-it-all/ challenge everything" attitude that accompanies adolescence.
The heart of the matter here is control: Control over blood sugar. Control of parent over child. Control of child over parent. The key may be to exercise as much self control on both sides.