sat scores have the lowest validity for predicting grades at which type of college?

SAT has less validity in the universities with very competitive admission standards. This is because to enter the students must have very similar SAT scores, and this does not allow to predict who will get the best grades or the best academic performance, because they are other factors those who could intervene in the possible academic success/failure.

I hope my answer can help you.

Smelly rocks sink in water haha!