Remember, though, that grades should not be used as rewards. Nor should they be used as affirmation, compensation, or validation. Grades should represent an honest report of evidence at this moment in time, nothing more. If we make them something more than that, we undermine the student’s maturation and any useful purpose for grading.
I'm working with several teachers on moving toward standards-based grading and we're starting to have conversations about grades themselves. I ask how they feel about zeroes, extra credit, completion, and makeup work. This article is a great primer and/or followup to those initial meetings.