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Tanmay has a great answer! Just to expand on that, freelancer.com is a great place to create a profile and start getting some work. But before you can get any work, they like you to showcase personal projects.
Which brings me to my main point, being in High School, you don't "need" internships, unless you want to get acquainted with a workplace. A good strategy for you in your spare time would be to research the software industry and start on small projects as quick as possible. Learn algorithms, learn certain languages that interest you.
Software is a huge industry with vast niches and connects with basically every other industry out there. There is no pressure for you to decide what you want to develop, just see what's out there and start programming, and answers will come your way, along with internship offers!
If you ever want to chat you can check out my profile, and if you want to meet over coffee in Redmond, I can find some time to meet.
A good place to start would be to talk to friends/family that work in the software industry. Most companies have good internships programs for new software engineers/developers.
However, most internship programs require the candidate to be enrolled in an engineering program. As a high school student, your opportunities may be limited. However, some companies just care about your software skills. You may want to start working on a resume and particularly showcase your software skills/projects/experience.
Nowadays, there are some small companies that want freelancing programmers to develop software for them. They usually advertise in the newspapers or on bulletin websites like craigslist. I don't know what your skill level is, but you might want to look at these positions to better understand what is expected level of skill/experience that companies are looking for.