A question to all high school and university students?

Okay, I want to go to Carleton for studying Aerospace Engineering/Science and get a masters in Physics and do all things revolving around it so I can go work at CERN/NASA. But I have a problem with mark. I got a 63 final mark for Grade 11 physics and I am in semester 2 doing chemistry. Also my math mark droped to a 77. So My question is what can I do, or start to do so I can fully learn all skills needed in all my high school courses (Especially Chemistry, Physics, Math, Computers, and the other important ones) and also get 90 average. I am only in Semester 2 for Grade 11 so I still have time. So please help me =D !!!