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Coming from someone who also likes programming, I think your extracurriculars are good. If you can make your projects available on the internet (Github is a good place), then mentioning them on college applications is a good idea. I don't know how Head Girl works at your school, but if it's similar to a student body position, then I'm sure it's good. Winning a debate competition is also really good and is a great thing to mention to demonstrate leadership in my opinion. Sure it can never hurt to do more, but what you have now is still good.