I've always understood the ACT as more about content and the SAT as more about aptitude, which means studying for the SAT is less useful than studying for the ACT.
You can teach test-taking strategies but those hardly require 2.5 years.
I agree some schools provide a better learning environment than others, and also engage in selective admissions either explicitly or via the socioeconomic status of the students' parents. Both of those could cause standardized test scores to improve but I wouldn't call it cramming.