I chuckle when I hear my friends call me spoilt. It's not my fault that I have a lot of iDevices, ey? ;D
I'm twelve. My first iPhone was a 3GS, when my dad got out of his contract. I was 10 at the time, and I needed a phone because I started to go out on my own to school, and all of the bricks we had were literally

broken. I only paid about £5 ($7.50) for it every month, with 500mb of data, as my calling/texting went through Pinger (which I still use today, with the same number.)
However, a few months later, the battery burst. The reason for that was because my dad actually accidentally dropped it before giving it to me, but I was still happy with the phone. It was my birthday then, and I accumulated enough money for a cheapy smartphone (December 2012.) So I bought the Samsung Galaxy Ace (I didn't really need an iPhone, as I had my own iPad 2, so yippe!)
My dad got a new phone on his birthday (August 2013) so I got to have his iPhone 4. He didn't really need a new phone; his iPhone 4 was in perfect shape, but the "Talking speaker" which was next to the FaceTime Camera, hardly worked. I also had an iPod Touch, which I got in July because of good grades.
I made a mistake of actually upgrading to the iPhone 4. It was terribly slow on iOS 7 when I upgraded it. It wasn't my fault that I upgraded it, someone put a passcode on my phone and I didn't know what it was!
I finally have an iPhone 4s (My mum upgraded to the Nexus 5) and I'm actually happy with it. Don't encounter lag anymore, so I love it!
You may call me spoilt, but I am not. I wouldn't have got my first iPhone if I got high grades, so I deserved it. I actually needed a new phone because my Android phone was falling apart; but I still kept using it, not demanding for a new smartphone. I wasn't happy with the lag that I got with the iPhone 4, and I wasn't expecting the 4S as I was saving up for a new phone. But I turned out lucky to have it. So, in conclusion, I think that, when your child is responsible enough to have an iPhone, he can have it. But make sure that it isn't a slow one that they'll be demanding a new one!

My phone had never been stolen before. They're all in a drawer, (Most of them) spotless.