Each school conference has their own standards. The D3 Conference is a very large tent. THey have everything from the NESCAC schools academically, to some state schools, such as those in Wisconsin.
Each school and conference servers a different populations of young men and women. There is some overlap. But each school or conference has different admissions standards, from some of the elite schools hardly anyone can get into down to If you have a diploma form a school in your state you gain addmitance. This is a good thing. all populations should be servered and given an opportunity.
But with the degree of diversity in D3, a minimum across the board would not be possible.