What makes for ivy league level extracurriculars? Meaning - say you have amazing SAT’s 1480-1520 but have 3.7 GPA from a super rigorous top private school. What sorts of EC’s will be enough to take you over the edge for serious Ivy consideration?
Everything and nothing.
There is no secret formula. If you composed a concerto which had its debut at Carnegie Hall by the NY Philharmonic, or won a Pulitzer prize, that would do it. For mere mortals? There’s no checklist which says “Intel semi-finalist adds another point to your GPA”. There are kids who get into Princeton who collect butterflies and do crafts; there are kids who get into Harvard with world class accomplishments.
Work hard and read a lot; foster your own interests and curiosity about the world; participate in a few things that are meaningful to you. After that- it’s a $%^& shoot for everyone, as you well know. Unless you’ve already composed that concerto- in which case, just send in your application and wait for the results to come in.
There are dozens of colleges which would be happy to have you just the way you are so don’t pursue EC’s you aren’t interested in for the sake of college admissions. Because if it doesn’t work- you’re stuck fencing when you’d rather have volunteered on a political campaign.
Do what you love, and do it in depth. Stretch yourself. Be creative. Take the activity up a notch or in new directions. Explore it. It isn’t about what you do so much as it is about the experience of challenging yourself and the growth, the journey/experience. Showing that challenge and growth, not just writing about it, makes a difference.
It’s unlikely you’ll guess correctly whether a college needs a harpist or a couple of clarinet players this year, or if it needs more football or more volleyball players. Hone your skills in activity you love, and you’re bound to go further than you could by doing something you don’t like nearly as much just to impress a random admissions officer somewhere.
If you are at a “super rigorous top private school” your guidance counselors will have the best advice as to what is needed to get into an elite college from that school.
Some of these private high schools have dedicated college admission counselors and privileged connections to elite private colleges, so you may want to ask those college admission counselors which, if any, elite private schools are realistic to apply to for you, and how extracurriculars can affect your applications there, since they may be able to give you better information that typical outsiders (including people on these forums and high school counselors at ordinary high schools). If that describes your high school, ask the college admissions counselors there.