Several countries have increased their legal minimum age for work in line with international conventions on child labor. We evaluated the effect of increasing the legal minimum age for work on school attendance in 3 low- and middle-income countries using difference-in-differences analyses. Increasing the legal minimum age for work increased school attendance by 3.0 (0.2, 5.8) percentage-points in Malawi, and 2.0 (0.2, 3.6) percentage-points in Colombia. In Malawi, we found a greater policy effect among girls compared to boys. In Colombia, the poorest tercile experienced the greatest improvement in educational outcomes. We found no evidence of an impact of increasing the legal minimum age for work on school attendance in Burkina Faso. Our findings suggest that increasing the legal minimum age for work has had a positive effect on educational outcomes in some low and middle income countries.