Yes, undergraduate students here can apply for early acceptance to the medical school in March of your sophomore year. Here is the link to the info: https://medschool.vanderbilt.edu/adm...early-decision
I don't think high school grades and ACTs/SATs are a factor. If they look at them at all, I doubt they are very important.
Other than obvious things they look at like your grades in the classes you've taken so far, I've heard that they like people who have gotten involved in research early. It is very competitive but not as impossible as some people think. Very few people are admitted, but given the number of people who apply your chances are not that bad. It's binding, but if you are accepted you avoid the whole MCAT/applying/interviewing stress-filled process...not to mention you are going to an amazing medical school