Elevation difference?

Here in Montana we regularly compete at over a mile of elevation, with one track in the state at 6200ft. above sea level. I know elevation helps sprints and hinders distance, but where is the line? Looking at times from MT, I’m beginning to think it’s at 400m for high school students and maybe the 800m for college. Any thoughts? Does running the 400m at 6000 feet help or hinder you? Would I run faster in the 400m at sea level?