High schools vary wildly in how rigorous they are, one high school you could get a 4.0 by taking four years of underwater basket weaving, another school you could get a 3.4 because you took AP Calculus/Bio/Physics your senior year and they were tough. Not to mention that sometimes your school weighs your GPA differently and that makes those numbers not make sense.
The SAT is administered by a private "not-for-profit" corporation (College Board) and doesn't test anything like history or science that most schools try to teach kids (well, probably all schools have a requirement). And every time someone wants to put together a national test as a replacement, it gets shot down (sometimes for good reasons, sometimes for not good reasons).
I did AP all four years of high school because I found the normal classes too boring, and my GPA probably would've been higher if I hadn't, but I got into college.
Even worse, grade inflation is going in the other direction. Not only do most schools have broad requirements for A and B level grades, but some give a 5 for an A if an honors course and a 6 for an AP or college level class.
The SAT is administered by a private "not-for-profit" corporation (College Board) and doesn't test anything like history or science that most schools try to teach kids (well, probably all schools have a requirement). And every time someone wants to put together a national test as a replacement, it gets shot down (sometimes for good reasons, sometimes for not good reasons).
I did AP all four years of high school because I found the normal classes too boring, and my GPA probably would've been higher if I hadn't, but I got into college.