medical assisting to rn?

I am currently in school for medical assisting (graduate in november) but would like to work my way to RN. I am not sure how to accomplish this. When I started looking I realized that all the schools require CNA first before going on to LPN then RN. Do you have to start at CNA then go to LPN then RN? Or can you just go to school for RN? I also never took ACTs or SATs in high school. I'm lost on how to get where I want to be! Anyone have any advice?