T20 and GPA

Hi, I’m currently a rising junior and I was wondering how big of an impact your GPA has on your overall college application process. I attend a magnet school and in my area it is known to give bad GPA’s. I got 3 B’s in my freshman year and 5B’s my sophomore year. Besides that I’m doing a cambridge diploma, similar to IB. I’m also in board for many clubs and I have has few internships. I want to go pre-med and I was wondering what my chances were of going to a T20 schools. Also, I have a high SAT and ACT scores.