Pretty hard to break iPhones....at least for me lol. I had an iPhone 4 and at work I dropped it around 6 feet onto concrete floors and never broke the pack or front glass panels. After 20 months it had one little nick on the bottom left near the home button.
My iPhone 6 plus has been in no case for most of the time and I've had it dropped on the floor at school, work, car and etc and beside a few dents and scratches it still has a perfectly fine screen minus a few hairline scratches. So even if he wanted to break his phone he might have to put enough pressure on it that Apple might be able to tell it was intentional.