I'm 19. Mine was a Christmas gift when I was 15. My dad was holding out until I turned 16 and was getting my license but he couldn't think of anything for me for Christmas, so he got me that

. In reality it was a good idea. I was a freshman in high school 10 miles from home (different city). The bus system from my town was TERRIBLE at the time, and the pay phones in the school worked maybe 2 days out of the year. Even better the secretaries in the office refused to let students use the office phones because that's what the payphones were for

So his lack of knowledge about his kid turned out to be good. I got my license a year later and that's when my phone really started getting used.
My sister is 15. She got her's for her birthday in September of her freshman year, when she was 14. I was still at the same high school as her, but got out earlier than she did, so she was dealing with busses. She's also very social, so it's a way to be able to meet up with her; she's generally out with just her friends, not friends and their parents. She actually just had her cellphone stolen from her gym locker on Tuesday, because she forgot to lock the locker, but the call from the school came in this morning that they'd caught the theif and gotten the phone back. Needless to say we're still working on responsibility with my sister. She did fine in the few days without her phone, but I'm assuming she's ecstatic to have her phone back
Except in rare situations I haven't figured out how a phone is really that necessary before high school. My stepsister did get one at 12 or 13, but that's because her mom was always forgetting to pay the home phone bill, and never had her cell phone on, so stepdad couldn't get ahold of her. But she's only supposed to use her phone for family calls