These are all excellent points! But, I think this is the discussion we should be having. I doubt we can get the data, but universities have data on both the p

These are all excellent points! But, I think this is the discussion we should be having. I doubt we can get the data, but universities have data on both the performance of students they have admitted (along with their schools) as well as their performance at the university. It seems like they could do their own analysis. You mentioned the question of what the A means. I wonder if just the act of working to get the A tells us something and that something may be more predictive of college success than the SAT/ACT. Or, another thing to imagine looking at would be say AP exam scores. I am biased, but I would imagine these would be more predictive than SAT/ACT and probably more informative than GPA. The question of change in major is interesting--but I think even the coarse question of say graduates/doesn't graduate would be interesting to see how it correlates with high school GPA (as compared to SAT/ACT) before delving into the more difficult cases that you rase.