Grading issue

I have this matter to handle.

I have 5 students who each takes a different number of courses. For each term, each gets a grade of A to D. Now after running for a few terms, I want to know collectively which one gets a higher overall grade. This is what I think:

As Grade A earns 100 points and Grade D earns zero, I assign 100 to each A, 67 to each B, 33 to each C and 0 to each D. Then for each student I add all the points together and divide the sum by the total number of data count. This is the overall grade in terms of a number. The one with the largest number has the highest overall grade.

This is my layman way to tackle the matter. Is there any statistical pitfall? Is there a more sophisticated way to do it?



Ambassador to the humans
So essentially you're just computing a GPA. The only thing I could think of is if the students don't take the same classes it might not be a perfectly fair comparison. Imagine Timmy takes three 1 credit courses on badminton and gets all As; Jimmy takes three 4 credit course on the physics of quantum neutrino fields and gets 2 As and a B. In your system Timmy is ranked higher but one might argue that the comparison by grade received isn't the best one to make.
Thanks for replies.

It is not intended to be a fair comparison. The purpose is to have an accountable way to decide who will get the year award for being better than the others in an overall sense. The differences among courses are not important for this exercise.

Yes, you are right. This is basically a GPA assessment.

Thanks, guys.
In that case, every choice you make will result in hard feelings. Whatever you choose, make it as transparent as possible. For that reason, I would lean toward your initial idea because everyone will understand it, whether they like it or not.