I'm 34.
I have a 10 year old son, he's going into 4th grade...I know that is younger than you, but I'll tell you what I would tell him if he asked for one:
1. No because you are too young and it's just too expensive of a phone to give to someone in 4th (9th) grade.
2. No because you won't really use it to it's full extent, which means a "regular" cell phone would suit your needs just as well. You don't have a job where you need to be able to access email, etc.
3. You need to learn the true value of things. Sure, it's nice to get an iPhone when you are so young, but then when you are older are you really going to appreciate how hard you have to work for things like this? Or are you going to be one of those people that gets things "just because" they are available. I grew up in an upper middle class family and saw a lot of my friends get everything they wanted, I had more than some people I knew, but certainly knew what it was like for my parents to say no. As an adult, I appreciate that because I've seen the other people grow up into spoiled adults who don't understand the concept of not having exactly what they want when they want it, whether they can afford it or not. Driving a 60K car means nothing when you are maxxed out on your credit cards and can barely make your minimum monthly payments.
I'm not trying to lecture you, and of course, the decision is yours and your parents...but you are young, give yourself something to look forward to when you get older.