How do you get longer legs?

I'm 13 and I want to become a model. My friend who is already a petit model told me that to become a model i need to have long legs or longer legs than the rest of my age group. I'm 5ft 2.5 inches so i'm one of the shorter kids in 7th grade so i really want and probably need to Develop longer legs than i already have, if there's any exercises that i can do to develope than PLEASE tell me!! thanks so much :))