There is an alternative that doesn't require explanation. It lets each student decide for themselves how much to put into each course and what grade might be acceptable to them and then work toward that goal. It is called cumulative grading.

Set a point total for the course, say 1000 points. Set a total for each grade level. Say 900 points for an "A" grade, etc. Whatever you think appropriate. Explain this in the syllabus.

Assign a point total for each piece of graded work, say 300 points for the term project, 200 for the final exam. Whatever, just let it come to the overall total. Explain the total for each piece when it is assigned. They need to know this for their own planning. Important things are worth more.

For each piece of graded work that they do, assign a value, up to the "value" of that piece: perhaps 285/300 for the term project.

The do enough work to earn their goal. Some might be encouraged to go beyond that goal.

I used this for many years successfully. But I added an additional element. If a student wasn't happy with the points I assigned, I permitted them to do the work again to earn part of the total back (not all, though). In order to ease my workload, each piece of work was submitted in a folder with the student's name and the previous marked work along with the new. In addition, they had to highlight the changes made from the original. This meant that I never got complaints about grading and those who needed extra work had a natural way to do it.

And, if they were happy with a B-, I didn't have to tell them I thought it was OK.

Extra Credit work is easy to assign for those falling short of their goals if you think this is needed. Give such things some points and grade as usual.

I didn't permit rework on exams, however, though exams weren't the largest part of their total workload. This was in CS.

There is an alternative that doesn't require explanation. It lets each student decide for themselves how much to put into each course and what grade might be acceptable to them and then work toward that goal. It is called cumulative grading.

Set a point total for the course, say 1000 points. Set a total for each grade level. Say 900 points for an "A" grade, etc. Whatever you think appropriate. Explain this in the syllabus.

Assign a point total for each piece of graded work, say 300 points for the term project, 200 for the final exam. Whatever, just let it come to the overall total. Explain the total for each piece when it is assigned. They need to know this for their own planning. Important things are worth more.

For each piece of graded work that they do, assign a value, up to the "value" of that piece: perhaps 285/300 for the term project.

The do enough work to earn their goal. Some might be encouraged to go beyond that goal.

I used this for many years successfully. But I added an additional element. If a student wasn't happy with the points I assigned, I permitted them to do the work again to earn part of the total back (not all, though). In order to ease my workload, each piece of work was submitted in a folder with the student's name and the previous marked work along with the new. In addition, they had to highlight the changes made from the original. This meant that I never got complaints about grading and those who needed extra work had a natural way to do it.

And, if they were happy with a B-, I didn't have to tell them I thought it was OK.

Extra Credit work is easy to assign for those falling short of their goals if you think this is needed. Give such things some points and grade as usual.

I didn't permit rework on exams, however, though exams weren't the largest part of their total workload. This was in CS.

It may be that not everyone in your course needs to understand the material at the same level. This might be especially true in the US where students have "majors" but also need to take courses outside the major to gain some general understanding. Such students have other, perhaps more pressing, needs.