i think taking classes is a really good idea, esp if they're in an area that interests you. really tho- why not enjoy the last summer before you're 16 and do some volunteer work somewhere? animal shelter, library, hospital, etc etc- those can go on college apps too
if you're taking CC classes, get to know your profs and see if any of them need a research assistant- somebody to do grunt work, or fill out paperwork, or even bring coffee/donuts, lol...my friend got one of those, and while the work wasn't "scienc-y", persay, she still got exposed to work environment
GL!