I've got Stop Homework in my Google Reader and there was a link in the post today to this article about why teachers shouldn't give a zero for an F in the 100 point system. And I have to say, ummmm, you missed the point a bit.
The authors agree that a 0 for an F in a typical 4-point GPA scale makes sense and I agree. But then they say that because it is ten points from A to B, B to C, and C to D in the 10 point/100 point scale often used in schools*, that it should be 10 points from D to F. The reason being that A is to B as 90 is to 80. I disagree.
The 4-point GPA scale is an attempt at a proportional scale. The 100 point scale isn't. I've always understood that the idea behind the 100 point scale is the "grade" represents the percentage of the information the student learned. If you answer 90% of the questions right on a test than you get a "90" and and "A"; if you earn 85% of the points, you get an "85" and a "B". (There is debate about whether mastering 70-79% of the material is truly "average" and deserving of a "C" but that's another question all together.) If you master only 50% of the information on a test then you are, or have been, considered failing with respect to that material. So is correctly answering 40%, or 22.5%, or 5% of the questions. It is very possible to earn less than 50% of the points on a given assignment.
There are problems with this system. A very low grade on one test can make it harder to pull one's grade up with later test scores (20, 70, and 90 give an average of 60, while 50, 70, and 90 give an average of 70) but if the goal is for the final grade to somehow represent the amount of information learned (particularly versus the amount instructed) than the 20 shouldn't become a 50 to maintain the proportionality of the letter grades. There is also a problem when an assignment is given a letter grade and not a numerical grade; in that case 100, 90, 80,70, 60, 50, and 0 may be the only appropriate numerical grades. 100 would be for an assignment that far exceeds standards, 90 exceeds, etc. with the 50 for the assignments that completely fail to meet standards and a 0 for failure to do a the assignment. I don't have much problem giving zeros for failure to do an assignment.
When I taught, as best I can recall, never gave a zero except in the case of no assignment turned in or cheating. If a student attempted to do an in class or homework assignment (and by "attempted" I mean they turned something in that had more than just their name on it) than that student got some points.) With one class I would vary the grading from simply a completion grade, number correct, and half-and-half on classwork/homework assignments to actually get them to do the work rather than just write down random things and turn it in. (They didn't care about their grades as long as they didn't, at report card time, get an "F". Very frustrating.) With the other classes their classwork/homework grades were based on the number of correct answers. I gave partial credit. I worked hard to get my kids points but sometimes there just weren't any to be had.
The long and short of it is, IMHO, the GPA scale and the 100 point scale are trying to measure or represent two different things. One is reasonably proportional the other a percentage.
A little on my grading philosophy: I used a modified "point pot" system in that each classwork/homework assignment, test, lab, and quiz was assigned a point value, usually one or two points per question except labs which were 10 or 20 points each. I calculated averages for each category (classwork, tests, quizzes, labs) by dividing points earned by points possible, and then used those averages to calculate their grade by weighting tests and classwork equally (30% each) and quizzes and labs equally (20% each). If a student had a passing test or classwork grade they would not get an F, even if mathematically that was the grade calculated. I believe that if a kid tries, (i.e. does the classwork) he shouldn't get a failing grade and if a kid knows the material whether he does any classwork/homework at all, he should not get a failing grade. I might not have given the student exactly the same grade as the classwork or test grade but he was guaranteed not to fail (i.e. 90% test, 10% classwork, 90% quiz, 10% lab scores might get a 85/B instead of a 51. Never happened, so, moot point.) I also tried to make sure my tests were fair and while I usually didn't do a rigorous item analysis (hard to do with only 12 students, max, per subject) I did throw out questions and/or give points back for bad questions.
*Just a little aside- The school district I grew up in had a "hard" grading scale. 100-94 A/4, 93-90 B+/3.5, 90-84 B/3,...,63 and below F. When I moved to Alabama my two C+s became Bs and my numerous B+s became As, and did that ever help my GPA. But to this day a 63 is failing to me.