@mbutler To add to what @goingsomewhereh wrote. Launching yourself into an awesome and meaningful EC would be a great idea and you should for sure do that, but you also have to realize that the colleges that you are applying to get between 20,000 and 100,000 applications a year, every year. The have seen it ALL. Most can spot a “trying to look good” phony EC a mile away. That is why most competitive colleges these days want a deep dive and/or authentic EC interest.
So while by all means look to pump up your ECs, I would also suggest you think long and hard about your “story.” How can you build a compelling narrative around what you already have done (and, if you can, do something “deeper” to build on that narrative.)
You have the scores. You need to give the schools (actually just one school that you want to attend. You can only go to one!) a compelling reason that you will add more to their campus than the next applicant with your scores and grades. By all means try to pump up your ECs, but try to do it by being unique, authentic and honestly interested. If you love sports and what you’ve done is sports - go all in. Build on it. Make your last year a “capstone project” of some sort around what you’ve done.
Then find a way, in your essays, to both explain yourself, your journey, your “story” and why that school is the place to complete that journey. From my experience watching kids apply to schools the last couple of years, those that have had the most success have found a way to convey to a school why they, the student, will add to that school in some small but tangible way, and more importantly, they have been able to show what specifically about that school will allow them, the student, to continue to build on their “story” or journey in an interesting, compelling way.
Just my .02 cents. Take with big dose of salt but it might be something to think about in the next few months.