I'm from Brazil, and here high school students don't have internships/research opportunities, but everyone I see online getting into my dream schools has had some kind of experience like those. Will it affect my admission if I don't have this kind of extracurricular?
I'm currently a junior at a public high school, just so you know.
In short, I don’t believe it will—nothing that is NOT required will be held against you. However, it certainly does help to have the experience, and thus, it becomes an “application booster”.
Take this from Cappex: “A summer job or internship shows maturity, responsibility and financial planning. Both look impressive on an application and your work experience will make it easier to apply for jobs and pursue professional opportunities in your undergraduate career and beyond.” (https://www.cappex.com/articles/applications/volunteering-internships-jobs-colleges).
And this from an online forum: The previous question, “Do internships help college applications?” The answer, “Yes, it would. Most of school or college students don't have access to internships, so having such an experience would make your application stand out.” (https://www.quora.com/Do-internship-helps-college-application)
Also, it would help to know what your interests are and your dream school—the context behind the question—for one to better answer this question. Wherever you go, you must keep in mind that you should not use internships as a star-badge to put on a college application—they should not be used for that intent, colleges won’t like this or think to highly of it. Instead, internships should be a self-desired initiative that shows your eagerness, your interests in a particular field of study.
Hope this helped a bit : )
To keep this community safe and supportive:
Thanks for the insight, you did help a lot. Just to clear things up, I wasn't planning on using any experience as a "star-badge" or describe myself differently than what I am; I really could not use such experiences on my applications since I have no way of living and enjoying them, and, if I had some way to do so, I would do it for the experiences themselves, not for resume-padding.