Banning Grades of ‘Zero’ from SchoolsPosted: August 5, 2013
A City Paper story last week reported on the move by Metro Nashville Public Schools to eliminate zero as a score on assignments, with 50 percent now becoming the lowest “F” grade a high school student can receive. The story elicited the whining one might expect from commenters about the dumbing down of education. Wrote one: “That is exactly what is wrong with our schools. So students who do not turn in an assignment still get half credit for doing it, even though they did nothing?” Another: “This is the most asinine policy I’ve ever heard. I thought child raising was moving away from everyone gets a trophy.”
In this case the school system has it right, and the whiners have it wrong. The reason isn’t pedagogy or tolerance for mediocrity or compassion or trophyism; it’s simple math. It is mathematically inane (and unethical) to grade on a 100 point scale and use zero as the marker of failure or non-performance.
Assume, for instance, that one connects percentage grades with letter grades by having 90 mark the dividing line between A and B, and 80 for B/C, 70 for C/D, 60 for D/F. (I don’t know that MNPS systematically uses these dividing lines but they are likely in the ballpark of how most people think about grades on a 100% scale.) Giving a zero on something throws into the student’s average a number for failing performance that is lower than the distance between C and D by a factor of five. It makes no sense to do that. One has to earn 150 on another assignment just to balance the the failure to achieve an average of 75.
Think about the 4.0 grade point average (GPA) scale common in higher education and some secondary schools. That scale makes sense because grade values of 4 (for an A), 3(B), 2(C), 1(D), and 0 are arithmetically equidistant, and because the number assigned for failing performance and non-performance is the same: zero. In linear mathematical terms, giving a student a zero on a 100-point scale where 60 is otherwise the D/F dividing line (so let’s call 55 a straight-up F) is the equivalent of giving a student graded on a 4.0 scale a grade point value of -5.5 and then averaging it in with all the other scores that range from 0.0 to 4.0.
The use of 100-point grading scales has always been idiotic for this reason, unless the teacher curves or concatenates the bottom end of the available range so that the lowest possible score (somewhere in the 50s, presumably) is in sync with the magnitude of steps across the overall range of grades. MNPS’s “let’s bottom out at 50” policy accomplishes this, making the system smarter, not dumber.
A version of this post appears on the Nashville Scene‘s Pith in the Wind blog.