Yes it is only for high school students going into their senior year. You can go to uscga.edu and search AIM summer program. It is in the first paragraph.
Only for rising seniors. I believe college students can register for visit programs, though, so it might be worth skipping a few days college. Personally, I was also a college student coming in. Stopped by just to see it real quick in seventh grade or something, and never stepped foot back on campus until my R-day!