How can I get rid of my anger?

I'm 13 years old and female and it seems I have a short temper or something because I strangled a girl for taking my pencil a few weeks ago. I try to calm down, but that's hard when people provoke you. I need to know how to calm down when I'm angry. I've tried that counting to 10 thing and even having a stress ball, but it doesn't help! In fact, I threw the stress ball at someone. I hate when people take my things and when they do I snap. I grabbed a boy by the coller of his shirt and threw him into a desk for taking my paper without asking and I tackled another boy to the ground for doing the same thing (and he was 5'6" and I'm only 5'0")! Then there was this girl who took my notepad and I beat her on the ground and pulled out her hair, so she know has a bold spot in the back of her head. It seems this has gotten out of hand and my family members edge me on, saying things like "kick their *** if they touch you!" So they're no help. I come from a naturally violate family too. My own mother has beaten a girl with brass knuckles before when she was younger and beat a lady at the supermarket up. (she herself and my uncle who was with her when it happened told me) and my older brother was known for throwing chairs at people when he was little, like 5th grade! So how do I get rid of my anger? I'm going to a new school this year and I don't want people to be afraid of me like at the old school.