CalTech for Grad School?

I'm currently a junior in high school right now and my dream is to get into CalTech. I've wanted to do so ever since I was little, but family troubles struck during my sophomore year and ruined my GPA. My chances of getting in right now as an undrgrad are scarce, but I'm being a little optimistic and considering attending the California Institute of Technology as a graduate student. I was wondering how I could do that. I have a great interest in physics and intend to peruse the field in college. Any advice?