You need to distinguish between admission for in-state, and out-of-state. Many public universities have some combination of grades and/or test scores that guarantee admission for in-state residents. I don't know of any that publish that information for out-of-state residents as well.
If your a Iowa senior, you need a certain score to get admitted into University of Iowa. I've also heard out of state students can get admitted also if they meet a certain score. I plan to apply to the school.