I second this. I grew up in a poor SE Asian country. There, we don't have prep school and such for SAT. But I went to US embassy library; borrow SAT prep books whenever they are available; make lots of photo-copies of some books (like Barron 3500 words) or just do practice tests at the library; and took these tests. I scored pretty well in SAT and SAT 2 subject tests that I won full scholarship at one of the good schools in the US.

It took me ~1.5 years to prepare for these tests (English was the hardest; math, physics, bio and chemistry are fairly easy because I finished high school there and the curriculum there is much tougher than the ones in the states), but in the end it's 100% worth it because without the scholarships, I'd never have been able to study in the US and be able to support my family (siblings and widowed mom) back home. If the admission committee decides solely based on holistic view like volunteering and other extracurricular activities, how could I compete with other well-off kids in the US for admission?