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Teachers’ cognitive skills are a key driver of international differences in student achievement
New study links student and teacher skills in math and reading across 31 countries

February 14, 2019—Research shows that in schools, teachers matter more than other resources when it comes to student achievement. Less clear is what makes a teacher effective—advanced degree attainment, experience level, and professional preparation are not consistently related to a teacher’s impact. In a new article for Education Next, Eric A. Hanushek of Stanford University, Marc Piopiunik of the ifo Center for Economics of Education (Munich), and Simon Wiederhold of the Catholic University, Eichstätt-Ingolstadt, report that teachers’ cognitive skills, on the other hand, are strongly related to student outcomes.

Hanushek, Piopiunik, and Wiederhold examined data from the Organization for Economic Cooperation and Development’s (OECD) Program for the International Assessment of Adult Competencies (PIAAC) survey in 2012 and 2015, which tested the reading and math skills of more than 215,000 randomly selected adults age 16–65 in 33 countries. They focused on the 6,402 test-takers in 31 countries—where they also had information on student achievement from the OECD’s Program for International Student Assessment (PISA)—working as teachers in primary and secondary schools. They compare teacher math and reading skills in each country to the skills of other adult workers in their country and to the skills of teachers in other countries. They also examine whether students score higher on PISA, on average, in countries where the median teacher has stronger math and reading skills.

Among the key findings:

Teacher cognitive skills vary widely across countries. By way of comparison, teachers in Turkey and Chile score well below Canadians with only a vocational post-secondary degree, while the skills of teachers in Japan and Finland are higher than those of Canadians with a master’s or doctoral degree.

The skills of U.S. teachers’ performance are slightly above average in reading but below average in math. Teachers in the United States perform worse than the average teacher sample-wide in math, with a median score of 284 points out of a possible 500, compared to the sample-wide average of 292 points. In reading, they perform slightly better than average, with a median score of 301 points compared to the sample-wide average of 295 points.

Student performance also varies across countries, especially in math. Students in top-performing Singapore scored 70 points above the sample-wide average of 498 on the PISA exam—the equivalent of nearly two school years. U.S. students scored well below that average at 484. In reading, Singapore students again earned the highest score of 534 compared to 445 for Chile, the lowest-scoring country in the sample. The U.S. score of 498 was not statistically different from the average of 497—leaving American students roughly one school year behind students in Singapore.

Teacher cognitive skills are strongly related to student performance both across and within countries. When teachers in a country have higher math skills than reading skills, students tend to perform better in math than in reading. Likewise, students tend to perform relatively better in reading when teachers have relatively higher reading skills. These effects are specifically driven by teacher cognitive skills and not the average skills of all adults in the country. The authors estimate that increasing teacher math skills by one standard deviation increases student performance by nearly 15 percent of a standard deviation on the PISA math test, and 10 percent of a standard deviation on the PISA reading test.

Teachers have stronger cognitive skills—and students achieve at higher levels in math and reading—in countries that pay teachers more for their skills. Teacher salaries, measured relative to those of similar college graduates, vary widely across countries, from 45% higher in Ireland, to 22% lower in the United States and Sweden. A higher teacher wage premium of 10 percentage points is associated with an increase in teacher skills of about one tenth of a standard deviation for a given level of skill, which carries through to higher student performance.

“These results speak to the potential value of increasing teacher pay but must be interpreted with care,” say Hanushek, Piopiunik, and Wiederhold. “Policymakers will need to do more than raise teacher pay across the board to ensure positive results. They must ensure that higher salaries go to more effective teachers.”

To receive an embargoed copy of “Do Smarter Teachers Make Smarter Students? International evidence on teacher cognitive skills and student performance” or to speak with the authors, please contact Jackie Kerstetter at The article will be available Wednesday, February 20 on and will appear in the Spring 2019 issue of Education Next, available in print on February 27, 2019.

About the Authors: Eric A. Hanushek is the Paul and Jean Hanna Senior Fellow at the Hoover Institution of Stanford University. Marc Piopiunik is an economist at the ifo Center for the Economics of Education at the CESifo Group. Simon Wiederhold is a professor at the Catholic University, Eichstätt-Ingolstadt.

About Education Next: Education Next is a scholarly journal committed to careful examination of evidence relating to school reform, published by the Education Next Institute and the Harvard Program on Education Policy and Governance at the Harvard Kennedy School. For more information, please visit

Last updated February 27, 2019