Shadow education and student achievement: Myth or reality? Global evidence from TIMSS 2019

Shadow education—paid supplementary tutoring outside school—has grown worldwide, yet its academic value remains contested. Using TIMSS 2019 data from 222,770 eighth-grade students across 38 countries, this study investigates whether participation in shadow education is associated with mathematics and science achievement. Ordinary Least Squares regression and Propensity Score Matching were used to adjust for observed background and study factors and to examine the stability of the observed associations. Overall, shadow education showed negligible associations with achievement: tutored students performed similarly to or slightly worse than peers, and incremental explained variance was near zero. Analyses by duration revealed no positive trends. While modest positive associations appeared in a few contexts, such as Japan, South Korea, and Turkey, these were inconsistent across subjects and countries. Findings suggest that participation in shadow education is not a strong predictor of higher mathematics or science achievement after adjustment for observed background and schooling factors.