Studies of gene-by-family socioeconomic status (GxSES) interactions in educational outcomes have yielded mixed findings. Building on a socio-contextual perspective, this study emphasizes that genetic influences are shaped not only by family environments but also by broader social forces, including gender and institutional context. Prior sociogenetic research, for example, suggests that early school tracking may suppress genetic influences. Using large twin registers from Finland, Norway, Germany, and the Netherlands, we analyzed gene-by-environment interactions by parental education and child gender, employing non-parametric gene–environment interaction models. Our results showed that genetic influences in Germany were weaker, and shared environmental effects were stronger, than in the other countries. We found no significant gender differences in the magnitude of genetic or environmental effects on educational attainment. Analyses of GxSES revealed that the form and strength of interactions depend on both gender and country context. In most countries, we observed a negative interaction among women, meaning that genetic influences were weaker among individuals from high-SES families. Among men, GxSES varied across contexts, appearing positive, negative, or absent. We conclude that country context and gender shape gene-by-SES interactions in educational attainment and may help explain the mixed results reported in previous GxSES studies.