And SAT as high school math exam itself I think is way too easy. They should design another test which can clearly distinguish top 1% or even 0.1%.from others

When I was in high school in California more than 20 years ago, SAT math alone was insufficient for admissions to STEM programs at mid-ranked and top-ranked universities. I was required to take the SAT Math IIC subject test, which went up to pre-calculus. We were also strongly encouraged to take calculus in high school. There are two AP Calculus exams: AB (which covers the first semester of university calculus) and BC (which covers the first two semesters).

There are already such tests. They're called International ___ Olympiad.