This paper examines the impact of school closures during the COVID-19 pandemic on student learning outcomes using global data from the Programme for International Student Assessment (PISA). The study finds that school closures led to significant learning losses, with math scores declining by an average of 12 points or 14 percent of a standard deviation between 2018 and 2022, equivalent to seven months of learning. The magnitude of learning loss varied by student characteristics, with greater losses observed for students in schools with longer closures, boys, immigrants, and disadvantaged students. Countries with the longest closures experienced the largest losses, up to 20 percent of a standard deviation, or 12 months of learning. The study also finds that the impact of school closures was more pronounced for students with lower achievement levels, while higher-achieving students experienced larger losses in countries with longer closures. The analysis uses PISA data from 175 million 15-year-old students across 72 countries, and incorporates information on the length of school closures from UNESCO and PISA. The study highlights the importance of addressing learning loss through targeted interventions, as the economic impact of these losses could be substantial. The findings underscore the need for policies that support learning recovery and reduce inequality in education outcomes.This paper examines the impact of school closures during the COVID-19 pandemic on student learning outcomes using global data from the Programme for International Student Assessment (PISA). The study finds that school closures led to significant learning losses, with math scores declining by an average of 12 points or 14 percent of a standard deviation between 2018 and 2022, equivalent to seven months of learning. The magnitude of learning loss varied by student characteristics, with greater losses observed for students in schools with longer closures, boys, immigrants, and disadvantaged students. Countries with the longest closures experienced the largest losses, up to 20 percent of a standard deviation, or 12 months of learning. The study also finds that the impact of school closures was more pronounced for students with lower achievement levels, while higher-achieving students experienced larger losses in countries with longer closures. The analysis uses PISA data from 175 million 15-year-old students across 72 countries, and incorporates information on the length of school closures from UNESCO and PISA. The study highlights the importance of addressing learning loss through targeted interventions, as the economic impact of these losses could be substantial. The findings underscore the need for policies that support learning recovery and reduce inequality in education outcomes.