I expect it would be difficult to get a meaningful internship as a HS freshman (unless perhaps you have family contacts). That said any extracurricular activity is valuable – seek out things you care about in your school or community and work to make a meaningful contribution during your HS years. As noted above, a part-time job is a well regarded activity as well.
Keep in mind that T20 schools often have single digit acceptance rates and can be quite different in terms of size, location, and many other important attributes. Over the next couple of years I recommend you do some more research and expand your horizons. There are tons of amazing colleges and universities out there.