What are my chances of getting into either Exeter or Andover in the states?

I am currently going into 8th grade so I still have about a year or two until I would apply. I’ve heard that schools like these look for good grades as well as experience in extracurricular’s. I currently attend a private school myself which is in the top 25 in my country. It’s been my dream to attend an elite boarding school in the states and I was wondering if I’d be qualified. My grades are average somewhere in the low 80’s but say I’d raise them up and get in the higher 80’s would that be high enough for schools like Exeter or Andover? I participate/ have had experience in extracurricular’s such as skiing, dance, swimming, ice skating. I also play two instruments including the piano and saxophone. So if I raise my grades up higher would I have a change of being accepted or is not so much? I am aware there are many other schools that could help me get into top universities but I’m very interested in these particular ones.