Yeah, I see where you're coming from (and it's true that the kids who go crazy in high school get it together for college -- I know; I'm one of them). But it's important to remember that we're dealing with a 13-year-old kid who probably doesn't need a phone anyway, and also that it's a goddamn privilege. You can make the argument that having them sign a contract is just being pragmatic and imparting a life lesson of another sort: when you live independently, you damn well better be ready to honor contracts to landlords, bursars, the telephone company and everything in between.
I would argue that a 13 year old is old enough to know right from wrong. And you're right he probably doesn't need a phone, much less an iPhone, so either 1) Don't give him such a privilege or 2) Trust his judgement. Meddling about and choosing something between 1 and 2 is not healthy.