The SAT is one of the most useless measures of knowledge or capability the world has ever seen. Standardized tests don't work, they've never worked and we know they don't tell us about a persons true intelligence. So if China wants to take a SAT for me, go ahead.
The SATs aren't for measuring intelligence. They're for measuring approximate education on a standard scale. That's their entire purpose - because if you're trying to compare two people who are from two different schools, how can you tell if candidate A's grade of a B+ makes him a better or worse student than candidate B's grade of a A in the same class? Assuming the same curriculum, that is. Is B better than A? Is there grade inflation going on (extremely common)?
In Canada, provinces have provincial exams - which basically test students on the curriculum material. All students take them to get their final mark for the course. There have been many cases where a student may score A/A+ on the course, and only a C on the provincial exam. A few cases have happened where they maybe score a C in class, but A-/B+ on the exams because the teacher grilled them hard, marked them hard and probably churned out better students.