I want to be a fashion designer?

I really want to be a fashion designer when i grow up. What should i do to accomplish that? How do i convince my parents to let me go to Parsons New School for Design, instead of a medical school when i go to college? (still in junior high) In the mean time, what should i learn about to become a designer? Is there anything i should practice? learn about? i also have NO IDEA how to sew, knit, crochet, etc. Help!