I think it's important to realize just how extremely non-obvious this is, though, for many high school sophomores/juniors.
I went to a decent high school and was in honors classes, and even I would have had zero idea test prep was even a thing, if a single science teacher hadn't randomly mentioned it in class once. I went to the school library and found the "Princeton Review" and practice exams and everything. I absolutely credit it with raising my score by probably a couple hundred points.
But I never would have discovered it except for that single teacher's offhand comment. I just assumed it would be a test that was an accurate reflection of your knowledge/intelligence, so as long as you were going to school, you'd just take the test and get your grade. If someone had pressed me, I probably would have said that test prep would be something kids in rich schools wasted their money on that wouldn't make a difference anyways. I just had no idea.
Yes, I absolutely agree that the SAT is the most attainable way for a poor kid to succeed at. I personally don't support the movements to remove standardized testing, not at all. But I also want to highlight how there's still an utterly gigantic step needed to reliably educate kids both about the importance of the SAT and how to prepare for it.
Very often barriers aren't even primarily a question of money/time/effort -- they're simply a question of awareness that an option even exists or that it matters.