I think the important part is clearly defining the 3 in a 1-5 system.

Like if 3 is "bare minimum for success", then 5 can be "perfect in every way we're measuring", and 4 can be "does more than the minimum but isn't perfect". Then 1 can be "absolute failure" and 2 can be "gets some things right, but not enough to satisfy the bare minimum."

That all seems pretty intuitive and accessible. Students who get 2s and 4s can go to the teacher during office hours to get more detailed insight on what they got right, and what they missed to fall short of the higher score. You don't need to be handing out 6, 7, 8, 9, like there has to be these very precise, measurable shades of 4.