Seems like at the moment high-school students in the US have to do two sets of exams - their normal high-school graduation exams, and also the SAT or ACT. Is that right? Why don't they use the results from one for the other? Use SAT for high-school graduation, or use high-school graduation results for university admission.
The SAT is also a thinly disguised IQ test, so it serves a different purpose anyway compared to high school grade records.
A lot of people have strong feelings against the SAT, but I actually think it's somewhat egalitarian. Before the SAT, prestigious colleges would only recruit from well-known feeder high schools whose curriculum was known to be rigorous. Since there is no unifying national curriculum, something like it is necessary so students from worse high-schools have a shot at getting into the nicer universities.