I have a weighted gpa of 4.13, have just started my junior year a month ago, and I am currently taking two APs and two honors courses and one language. I understand that essays and short answer responses factor into my getting admitted, but I'm deliberating which extra-curriculars I should take.
Ask your social studies teachers about Boys and Girls State. It's a prestigious program offered for rising seniors, so it would be an over-the-summer program. You get to learn about government while living on a university campus for a week and for free. It's impressive on your college apps, plus it's really fun and you will make a lot of friends there!
As for after-school activities, joining debate club and government clubs in general may show your leadership skills to colleges, which most of them are looking for. Any other extracurriculars should reflect your interests, not just being a bunch of random clubs that look like you did it just for the college app. They want to see what you're passionate about, so try to join clubs that are related. For example, someone who's in theatre may also want to join singing or band. It shows you have a clear interest in performing arts. Hope this helps!
As mentioned by @gumdropsnlollipops above, it really depends on your interests and passions. For example, I'm really into engineering and STEM, so I'm doing robotics, math team, and aeronautics but I'm also doing some other things I enjoy, such as tennis, Asian Culture Club, and FBLA. My advice is to find what you enjoy, what you want to do in the future, and find correlation between them to help you. I my opinion, it's better to do a few clubs that you really dedicate yourself than have a huge scatter of extracurriculars. Colleges want to see who you truly are, and what you enjoy, which is what applications are all about. Good luck!
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@gumdropsnlollipops Thanks! I currently am not exactly eligible to join the Girls State thing, but that sounds cool. I'm currently in the Yearbook and Newspaper Club and wanted to sign up for the Math Team and DECA. However, I feel like these clubs seem too arbitrary, and I don't want any ivy league schools to get the wrong impression. Like you mentioned, I merely don't want them to believe I'm participating for the sole purpose of looking good to them.