As one college admissions official directly told me: the SATs are the only way that we can compare a vast number of our applicants.
He elaborated: we have a hard time telling the difference between grading systems at different high schools and parents vastly overestimate how much going to a “good” high school matters. For example, regarding two excellent high schools,
How does a 102 average at Lyme-Old Lyme High School contrast with a 4.2 at East Lyme High School?
More problematic, how do you compare the valedictorian at a less competitive high school than Lyme-Old Lyme School or East Lyme High School with someone ranked in the top 10 at either school?
Classes? Most of the kids at the top of each high school take the most competitive classes the school offers.
Activities? Every school has Presidents of clubs, Captains of sports teams, stand outs in music and leads in school plays
It is not the only weapon in one’s college arsenal.
But if you have a student from a great high school such as Lyme-Old Lyme or East Lyme then it makes sense maximize SAT scores.