Questions and concerns about art school, coming from a high school senior.

I'll try to get into detail here so that you guys can understand my perspective, but I'm mostly expressing my concerns/questions, so feel free to answer.

First let me start off by saying that this is not about "how to get into art school", or "If art school is worth it". I've talked to people that look through admissions/portfolios, and I've talked to teachers, so I think I have a fairly good grasp on that.

I don't think I'm too bad at art, and I think I have a grasp on most of the "basic" mediums (painting, graphite, charcoal, ink, etc.). I don't at all want to sound egotistical, but I have won a couple of awards within my school (not crazy ones, but a sketchbook award and a digital art award) and I'd say I'm up there for someone within my grade (I know a couple of people who are pretty nuts).

Here's some of the stuff I did this summer during some programs (excuse my terrible camera and photography):

Imgur Collection

One thing that I have been worrying about, was whether or not I should be working with a bunch of different mediums, versus simply focusing on drawing or painting exclusively and "mastering" that. Should I be training myself in multiple mediums before art school, so that I'm not completely clueless when we have to use a new medium (not sure if you actually have to do that)? Should I get really good at drawing and practice things like perspective and anatomy? I'm not sure.

Sometimes I also feel like I didn't start young enough, or that I should be taking life drawing classes as of right now or starting when I was a little younger. I see videos of artists who show their work from when they where in high school or even prior (I get that they probably only show their good stuff, but that's beside the point), and they usually tend to be pretty good, which can be inspiring and discouraging at the same time. Should I be taking life drawing classes (or any other kind of class) in order to prepare for art school?

I'm also just wondering if anyone had any suggestions on how to better prepare myself for art school (as in skill wise)? I don't religiously practice every day, and I don't consistently go to art classes, outside of school that is, so I'd say I'm about half self taught. Any suggestions would be great.