Is it too late for an ivy legue university ?

Right now I live in Iran and I'm a sophomore. My average grade this year was 18.5 ( A I suppose) last year I got an average of 19.32 ( out of 20) I speak 3 languages fluently and do many extra curriculum activities. I'm continuing my high school in Scotland from September .if I do really well in Scotland with my A levels will I have a chance at an ivy legue university like Princeton despite my grade of 18,5? Or they look at each subjects grade individually instead of an average grade of allsubjects all together?( I got 16 in maths, 20 in physics and 15.5 in chemistry out of 20)