Do I have high enough grades to transfer to the University I want?

Okay, i'm currently a senior in high school and about to graduate in about 2 months. Throughout my first 3 years of school I never did well, and got very bad grades. I started improving a little toward the end of my junior year, then once I became a Senior I became very serious and this whole year I haven't gotten anything below a B+. Now, my goal is to get nothing other than an A throughout city college and for the rest of my senior year. I would like to apply to Colombia University if I succeed in this goal, but will they still look at my high school grades? Will I have a chance in still getting in? & do I need to write a resume? Or is that only for post grad school? Thank you!