The study examines the impact of school closures during the COVID-19 pandemic on primary school performance in the Netherlands, using rich data from approximately 350,000 students. The research compares student progress before and after lockdown, using national examinations that occurred both before and after the closures. Despite the relatively short lockdown (8 weeks) and the Netherlands' equitable school funding and high broadband access, the study found a learning loss of about 3 percentile points or 0.08 standard deviations, equivalent to one-fifth of a school year. This loss was most pronounced among students from less-educated homes, with losses up to 60% larger than the average. The findings suggest that students made little or no progress while learning from home, and that losses could be even larger in countries with weaker infrastructure or longer closures. The study used a difference-in-differences design, adjusting for confounding factors such as trends, testing dates, and sample composition. It also used propensity score rebalancing, maximum-entropy weights, and fixed-effects models to ensure robustness. The results indicate that the learning loss was primarily due to the cumulative impact of knowledge learned rather than temporary influences on the day of testing. The study also found that the effect was not distributed equally, with disadvantaged students disproportionately affected. The research highlights the importance of social investment strategies to "build back better" and enhance resilience and equity in education. It underscores the need for policies that address the long-term effects of the pandemic on student learning and well-being. The findings suggest that the pandemic's impact on education is significant, with learning losses that could be even more severe in other countries with less prepared infrastructure. The study provides valuable insights into the challenges of remote learning and the need for equitable access to educational resources.The study examines the impact of school closures during the COVID-19 pandemic on primary school performance in the Netherlands, using rich data from approximately 350,000 students. The research compares student progress before and after lockdown, using national examinations that occurred both before and after the closures. Despite the relatively short lockdown (8 weeks) and the Netherlands' equitable school funding and high broadband access, the study found a learning loss of about 3 percentile points or 0.08 standard deviations, equivalent to one-fifth of a school year. This loss was most pronounced among students from less-educated homes, with losses up to 60% larger than the average. The findings suggest that students made little or no progress while learning from home, and that losses could be even larger in countries with weaker infrastructure or longer closures. The study used a difference-in-differences design, adjusting for confounding factors such as trends, testing dates, and sample composition. It also used propensity score rebalancing, maximum-entropy weights, and fixed-effects models to ensure robustness. The results indicate that the learning loss was primarily due to the cumulative impact of knowledge learned rather than temporary influences on the day of testing. The study also found that the effect was not distributed equally, with disadvantaged students disproportionately affected. The research highlights the importance of social investment strategies to "build back better" and enhance resilience and equity in education. It underscores the need for policies that address the long-term effects of the pandemic on student learning and well-being. The findings suggest that the pandemic's impact on education is significant, with learning losses that could be even more severe in other countries with less prepared infrastructure. The study provides valuable insights into the challenges of remote learning and the need for equitable access to educational resources.