The Tyranny of the Norm (or, it’s normal to be different)

According to the Boston Globe (“Student takes his C to federal court,” October 4, 2007), a student at the University of Massachusetts-Amherst has gone to court to challenge a grade in one of his courses. The student determined he had done “A” work in the course but, because the final grade was computed “on a curve,” he got a “C” for his final grade. Lots of high school and college teachers grade “on a curve.” It’s more or less assumed that the bell curve provides a natural description of most human behaviors, including academic performance. The idea that, in general, human behavior distributes “normally” is a powerful idea that stands behind whole-class instruction (most kids cluster around the average), special education (students who depart significantly from the norm require a “special” education), educational testing (students are often compared to the “average” student at their grade level), educational research (statistical comparisons between groups or instructional interventions are based on the mean), and, sometimes, grading practices.

One of my doctoral students and I have been researching the history of the normal curve. Almost everyone assumes that the normal curve is an accurate model for representing variation in human behavior, but does the evidence actually support this common-sense assumption? As it turns out, some physical characteristics like height do distribute along a bell-shaped, normal curve. The vast majority of human behaviors do not, however, distribute normally. Weight doesn’t. Running speed and reaction time don’t. It’s not clear that intelligence or academic achievement distribute normally, either. Standardized tests are designed to produce normal distributions so the degree to which traits like intelligence and academic achievement distribute normally says more about the skill of the people who construct tests than it does about the human condition (and, even then, actual test scores often do not produce normal distributions). So, as it turns out, normal distributions are not the norm and this has been apparent to a few statisticians and social science researchers for over 100 years.

If the normal curve is a myth, as we believe that it is, then beliefs and practices based on the assumption of normality must be challenged. One particularly troubling practice that emerges from the “myth of normality” is the use of means (or averages) to represent groups of people, especially school children. The problem of using averages to represent the performance of children in our schools is that averages obscure the natural variation that characterizes the behavior of human beings. The claim that boys do less well in school than girls does not consider the fact that many boys do very well in school (better than most girls) and many girls do poorly in school (worse than most boys). Similarly, research on fourth grade readers or students with learning disabilities, for instance, obscures the individual needs of real children who are not statistical averages.

The assumption of normality has led to a range of educational practices and research that ignore the variety of ways children learn and the wide range of experiences they have in and out of school. We need to replace the notion that it’s normal to be average with the idea that it’s normal to be different. This will lead us to shift the focus of research and instruction from the mythical average student to the needs of individual learners.