Teacher cognitive skills shifted notably over the last decade. Using PIAAC Cycles

1-–2 for 25 countries, we document how the level, dispersion, and relative standing of

teachers’ numeracy and literacy evolved within countries. The descriptive evidence

reveals large heterogeneity: some countries saw teacher-skill declines of about

one standard deviation, while others improved; and teachers’ position within the

tertiary-educated workforce moved by 15+ percentile ranks in several countries—

consistent with substantial changes in selection into teaching. We then ask which

policies and labor-market conditions (e.g., relative teacher wages, outside options

for high-skilled women, and teacher status) are associated with these shifts. In a

second step, we relate these country-level changes in teacher skills to changes in

student achievement using rich PISA microdata in mathematics and reading. For

identification, we exploit within-country variation across subjects and over time,

testing whether students in countries where teachers gained in numeracy relative to

literacy also improved more in math relative to reading. Data on subject-specific

skills in PIAAC for the overall population and for detailed occupations enables a

set of robustness checks and placebo tests that help separate changes in teacher

skills from broader skill changes within countries. Understanding how and why

teacher skills evolve internationally–—and whether these changes translate into

student achievement–—matters for policies aimed at strengthening teacher quality

and improving educational outcomes.

This study combines two OECD datasets to examine how changes in teacher cognitive skills relate to changes in student achievement. We use PIAAC Cycle 1 (2012, 2015) and Cycle 2 (2022, 2023) to construct country-level measures of teacher numeracy and literacy skills across 25 countries (~9,500 teachers). These are linked to PISA microdata (2009, 2012, 2018, 2022) covering approximately 860,000 students. We implement two complementary identification strategies. First, a baseline panel model exploits within-country variation over time: Aicwk = β Tc,s(w),k + X'icw γ + αc + λw + εicwk where student achievement depends on teacher skills, with country and wave fixed effects eliminating time-invariant confounders and global shocks. Second, a within-country, across-subject, over-time design tests whether countries where teachers gained in numeracy relative to literacy also improved more in mathematics relative to reading: (Aicw,math − Aicw,read) = β (Tc,s(w),num − Tc,s(w),lit) + X'gapicw γ + αc + λw + uicw This triple-difference approach (country × time × subject) eliminates all time-invariant country factors and reforms affecting both subjects equally. Controls include student/family characteristics, school resources, instructional time gaps, and parental skill gaps. Robustness checks include placebo tests using other occupations and empirical Bayes shrinkage for measurement error.

Our descriptive analysis reveals substantial cross-country heterogeneity in how teacher cognitive skills evolved between PIAAC cycles. While pooled averages show minimal change (−1 point numeracy, −2 points literacy), individual countries experienced dramatic shifts: Lithuania declined by 30 points in numeracy and 25 in literacy, while Japan and the Netherlands gained 19-20 points in numeracy. Teachers' relative position within the tertiary-educated workforce shifted by over 15 percentile points in multiple countries, indicating meaningful changes in selection into teaching. These shifts occurred against widespread student achievement declines, particularly in mathematics, motivating our core research question: do changes in teacher skills translate into changes in student performance in a subject-specific manner? Based on prior cross-sectional evidence (Hanushek et al., 2019) and our identification strategy, we expect to find positive relationships between teacher skill changes and student achievement changes. The within-country, across-subject, over-time design should reveal whether countries with relative gains in teacher numeracy versus literacy show corresponding improvements in mathematics versus reading performance. Additionally, we expect that changes in labor market conditions—particularly women's access to high-skill occupations and relative teacher wages—correlate with changes in teacher cognitive skills, providing insights into policy levers for strengthening teacher quality. Note: All results will be available by conference presentation in August 2026.

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