What you are doing seems to be like 'focus correcting," a method of
grading English papers concentrating on a specific issue. In this method,
when a class (or most students) have mastered the first areas, they are
"dropped' and assumed to be always included and another area is zeroed in
on. We use evaluation sheets at the high school for all projects where the
criteria for grading are given at the start of the project with point
assigned to various items. It helps some, too. I think grading is always a
problem and my least favorite part of teaching.