future director....?

I am a 15 year old girl from Australia (where I live). I am in yr 10 and am really starting to think about what i want to do for a career. I am caught up between law (my realistic choice) and directing films (my wish). I know a lot about what grades I would need and where I would go for my undergrad, then postgrad etc if I pursured law but I don't really know about directing. My question is: Could anyone tell me about where to go and what to do for directing? I want to do the directing course at NIDA but that can noly be taken by people 22 years and above. So basically from when I amd 18 till when i am 22 I will need to be doign somethign which will add to my experience and help me get into NIDA etc. Does this mean i do a film course at some film school or what...? Please help me out lol Thanks