This paper investigates the relationship between early childhood nutrition and academic achievement using a unique longitudinal dataset from the Philippines. The study follows a large sample of children from birth until the end of primary education, examining the impact of malnutrition on school performance. Key findings include: 1. **Malnourished Children Perform Poorer**: Malnourished children perform worse in school, even after controlling for unobserved heterogeneity. 2. **Early School Entry**: Part of the advantage of well-nourished children comes from entering school earlier, giving them more time to learn. 3. **Learning Productivity**: The rest of the advantage is due to greater learning productivity per year of schooling, rather than increased effort in homework or attendance. 4. **Economic Significance**: Despite these findings, the relationship between nutrition and learning is not likely to be crucial for nutrition policy or economic growth. The study uses a sibling difference approach to address potential spurious correlations and endogeneity issues. It also discusses the delayed enrollment and selection bias in the data, which are important for accurate estimation. The results suggest that a one standard deviation increase in height-for-age raises achievement test scores by about 5 points, equivalent to spending an additional four months in school. The indirect effects of nutrition, through delayed enrollment and reduced grade repetition, further enhance this impact.This paper investigates the relationship between early childhood nutrition and academic achievement using a unique longitudinal dataset from the Philippines. The study follows a large sample of children from birth until the end of primary education, examining the impact of malnutrition on school performance. Key findings include: 1. **Malnourished Children Perform Poorer**: Malnourished children perform worse in school, even after controlling for unobserved heterogeneity. 2. **Early School Entry**: Part of the advantage of well-nourished children comes from entering school earlier, giving them more time to learn. 3. **Learning Productivity**: The rest of the advantage is due to greater learning productivity per year of schooling, rather than increased effort in homework or attendance. 4. **Economic Significance**: Despite these findings, the relationship between nutrition and learning is not likely to be crucial for nutrition policy or economic growth. The study uses a sibling difference approach to address potential spurious correlations and endogeneity issues. It also discusses the delayed enrollment and selection bias in the data, which are important for accurate estimation. The results suggest that a one standard deviation increase in height-for-age raises achievement test scores by about 5 points, equivalent to spending an additional four months in school. The indirect effects of nutrition, through delayed enrollment and reduced grade repetition, further enhance this impact.