What is the signal Harvard uses to test for intelligence or academic competence? So far I only have learned that SAT and ACT are not it. Whaat is?
There does not exist a meaningful test of general intelligence that outputs a number that is equally meaningful to people from all socioeconomic (or even cultural) backgrounds. Similarly, there does not exist a meaningful test of academic potential (aside from a student's existing academic record).
College entrance exams are a scam meant to make money for the people who manufacture them. I say this as someone who did pretty well on every standardized exam I took, and felt guilty because I knew students who performed worse and had fewer college prospects than I did because of it, even though I knew they were better students who would easily out-perform me at the more prestigious institutions to which I was admitted in most meaningful metrics.