13 but not allowed facebook?

[Meg]

I'm 13 years old but still my parents wont let me get facebook. I understood when I was younger but now I have been 13 for a long time and they still haven't allowed me to get it. I will be sensible on it, no swearing, no bullying, no adding anyone who I don't know. They know that I have yahoo answers, ask fm and even youtube but they still wont let me get facebook! Surely facebook isn't as bad as youtube where anyone can see and hear you or ask fm where people can bully you on anonomous and where there is lots of swearing and rudeness. I don't understand why they wont let me. I have tried to tell them that I haven't been invited to parties etc because of not being on facebook and that many of my friends who I don't have the number of who went to my primary school have facebook and then I can keep in touch with them. My parents just said in return to that "why don't you just send them a letter." I am not going to make an account behind there account as I know that this would be wrong but can you think of any ways to try and perswade them? Thanks xxx
I also already use tumblr xx
Also my mum and dad both have facebook so they know that there is a privacy button and they could add me to make sure that I am being safe on there