## A Brief History

*Excellent, Average*, and

*Poor*. Another was the familiar five-point scale of

*Excellent, Good, Average, Poor*, and

*Failing*, or

*A, B, C, D*, and

*F*(Johnson, 1918; Rugg, 1918). This decrease in the number of score categories led to greater consistency across teachers in the grades assigned to student performance.

## A Modern Resurgence

*C*) and establish 60 or 65 as the minimum threshold for passing. This practice dramatically increases the likelihood of a negatively skewed grade distribution that is "heavily gamed against the student" (Carey & Carifio, 2012, p. 201).

## Problems with Percentage Grades

## Logistics

## Accuracy

*standard error of measurement*. This statistic describes the amount by which a measure might vary from one occasion to the next using the same device to measure the same trait. For example, suppose the standard error on a 20-item assessment of student learning is plus or minus two items. That may not seem like much, but using a percentage grading scale, that would be a range of 20 percentage points—a difference in most cases of at least two letter grades.

*Excellent, Average*, and

*Poor*). But in the absence of a truly accurate measuring device, adding more gradations to the measurement scale offers only the illusion of precision. When assigning students to grade categories, statistical error relates to the number of misclassifications. Setting more cutoff boundaries (levels or categories) in a distribution of scores means that more cases will be vulnerable to fluctuations across those boundaries and, hence, to more statistical error (Dwyer, 1996). A student is statistically much more likely to be misclassified as performing at the 85-percent level when his true achievement is at the 90-percent level (a difference of five percentage categories) than he is of being misclassified as scoring at an

*Average*level when his true achievement is at an

*Excellent*level. In other words, with more levels, more students are likely to be misclassified in terms of their performance on a particular assessment.

## Percentage Grades vs. Percentage Correct

## The Distortion of the Zero

*B*to an

*A*in most schools that use percentage grades requires improving only 10 percentage points at most—say, from 84 to 94 percent. But to move from a zero to a minimum passing grade requires six or seven times that improvement, usually from zero to 60 or 65.

## What's the Alternative?

*Below Basic, Basic, Proficient*, and

*Advanced*) and with the four-point rubrics that many teachers use in judging students' performance on classroom assessments.