Friday, September 1, 2017

Mathematics as Peacock Feathers

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Mathematics occupies a privileged position in our educational system, generally equated with English language facility—reading and writing—for emphasis within the K-12 curriculum, in curriculum reform efforts such as Common Core, in admissions testing with SAT and ACT, and in college graduation requirements. Why? An important recent article by Daniel Douglas and Paul Attewell, “School Mathematics as Gatekeeper,”[1] draws on data from the Education Longitudinal Study of 2002 (ELS:2002) [2] to explore this question.

A common response is that in today’s technologically driven society, mathematical knowledge is more essential than ever. Yet, as the authors document, the fact is that few workers, even in those jobs that require a bachelor’s degree, use mathematics at or above the level of Algebra II on a regular basis.

Of course, no one argues that actually factoring a quadratic or finding a derivative are essential skills for today’s workplace. Instead it is the habits of mind that learning mathematics instills that are considered so important. Douglas and Attewell look at the other side of this connection. It has been extremely difficult to demonstrate that mathematics instruction does lead to the development of logical thinking and effective problem solving, but society does recognize those who are successful in mathematics as talented individuals who are primed for success. The authors explore the role of mathematical achievement as a signal that a prospective student or employee is going to succeed, just as a peacock’s feathers signal a male capable of fathering strong offspring (Figure 1).

Figure 1. From Bob Orlin’s “The Peacock Tail Theory of AP® Calculus.”

Signals are important. Those who are believed capable of succeeding are more likely to get the support and encouragement they need to succeed. Douglas and Attewell were able to draw on ELS:2002, a ten-year longitudinal study of survey data and transcripts of 15,000 U.S. students, to test whether mathematical achievement in high school has such a signaling effect. Able to control for the common variables associated with success: general academic performance in high school, motivation, effort, academic involvement, gender, race/ethnicity, socio-economic status (SES), and parental education, they took as their null hypothesis that mathematical achievement—especially having studied precalculus or calculus in high school—would add nothing to the chances of being admitted to and graduating from a four-year college program.

That null hypothesis was firmly rejected with a p-value less than 0.001. Controlling for all of those other factors, taking trigonometry or precalculus as the last high school math class was associated with increased odds of attending a four-year college, close to two times those of students whose last mathematics class was Algebra II. The odds of attending a selective college were doubled. Calculus in high school is an even stronger signal, associated with the increased odds of attending a four-year college by a factor of two and a half, and attending a selective college by a factor of three. Again controlling for all of these other variables, completing any of these courses nearly doubled the odds of earning a bachelor’s degree.

In the other direction and still controlling for all other factors, terminating high school mathematics at Algebra I was associated with far lower odds of attending a four-year college—by a factor of one half. The odds of earning a bachelor’s degree among students completing only Algebra I were about a quarter of that for students for whom Algebra II was the highest mathematics course taken in high school.

Reporting marginal effects, the authors note that students taking precalculus as the last high school mathematics course were 12 percentage points more likely to attend a four-year college than those for whom Algebra II was the last class. A precalculus class also raised the likelihood of attending a selective college by 12 percent, and of earning a bachelor’s degree by nine percent. Similarly, taking calculus in high school boosted the likelihood even further: 16 percent for four-year colleges, 18 percent for a selective college, and 10 percent for earning a bachelor's degree.

Perhaps surprising is the fact that this signaling effect is strongest for students of high SES. Using a composite score of mathematical ability as measured by the ELS:2002 standardized test in mathematics and the highest mathematics course taken in high school, students scoring one standard deviation above the mean increased their likelihood of attending a selective college by 12 percent. For students with high SES, it increased by 25 percent. It is important to note that while these findings are statistically significant associations, they should not be interpreted as statements of causality.


The authors emphasize the irony of the very strong signal sent by advanced work in high school mathematics given how small a role it plays in actual workforce needs. It is my personal belief that the strong signaling effect of mathematical achievement points to something real, an analytic ability that goes beyond the other talents for which this study controlled: general academic performance in high school, motivation, effort, and academic involvement, but that the signal has been amplified beyond reason. This has important implications.

The common perception that calculus on a high school transcript helps a student get into a selective college is supported by these data. It also appears to improve the chances of completing a bachelor’s degree. Given that this effect is strongest for students of high SES, those with parents who are best positioned to push to accelerate their sons and daughters, the trend to bring ever more students into calculus at an ever earlier point in their high school careers is rational. Rational does not mean desirable, or even necessarily appropriate, but it does mean that trying to counter the growth of high school calculus will require more than recommendations and policy statements. If misapplied acceleration can do harm, as many of us believe, we need convincing evidence of this.

The work of Douglas and Attewell should also inform the debate over requiring Algebra II in high school. Those who oppose this as a requirement for all students point out that few will need the skills taught in this course; this perspective is highlighted by the study authors, though they do not believe mathematics requirements should be summarily dismissed. The problem is the self-reinforcing signal sent by not having Algebra II on one’s transcript. Their work also points to the importance of making precalculus and calculus available to all students who are prepared to study them. Lack of access in high school does more than postpone the opportunity for their study; the evidence suggests that it actually damages chances of post-secondary success.


[1] Douglas, D. and Attewell, P. (2017). School mathematics as gatekeeper. The Sociological Quarterly.

[2] National Center for Education Statistics (NCES).