A question about acting?

I think your big stage schools in London are more for college/university students? I think your best change right now is to get yourself an agent. Try joining Stage Coach or a big drama school like that and when you eventually finish your GCSEs / A levels then apply for RADA :) Do get yourself noticed though, I remember how much I loved acting when I was 15! And I got myself in as many shows as possible, good luck!