The Grade Doctor says:

Not a reasonable analogy. The basic problem with zeros is their use with the calculation of
the mean in unequal difference scales. If your district uses the most common grading scale
 A  90100%, B  8089, C  7079, D  6069 and F  below 60, a zero is not an F it is
a K. Also we teach in grade 5 math that the mean is an inappropriate measure of central
tendency when there are outlier scores and zero is the ultimate outlier. If you change to a
50 point scale with five 10 point groups or a 4 or 5 point equal difference scale then your
colleagues analogy is more reasonable and you can use zeros but NOT when you are usin
an unequal difference scale.
