Hi there, I’m also a junior in high school, recently committed to play baseball at MIT. Sports at MIT are no joke (I turned down many many D1 schools, including Harvard and Notre Dame), so you still have to be rather good at your respective sport. The weight of the sport can be dependent on the type of sport. For example, football may carry more weight than, say, squash. Your scores are great and all, but definitely not enough to get into MIT on their own right.
From what I’ve heard from the head coach in my case, sports hold roughly the same weight as a decently significant extracurricular, but will not allow for admission on their own.
If the coach is truly interested, he/she will make it rather clear.