School closures due to COVID-19 have left over a billion students out of school. Governments are pursuing a variety of approaches to mitigate school closures. At the same time, all countries are undergoing the largest economic contractions of our lifetime, reducing public budgets and household incomes. What effect might this perfect storm have on schooling attainment and learning? This paper presents the results of simulations considering different lengths of school closure (3, 5, and 7 months) and different levels of mitigation effectiveness (mostly remote learning), resulting in an optimistic, intermediate, and pessimistic global scenario. Using data on 157 countries, we find that both the global level of schooling as well as learning will fall. COVID-19 could result in a loss of between 0.3 and 0.9 years of schooling adjusted for quality, bringing down the effective years of basic schooling that students achieve during their lifetime from 7.9 years to between 7.0 and 7.6 years. Close to 7 million students from primary up to secondary education could drop out due to the income shock of the pandemic alone. Without compensatory actions when children return to schools, students from the current cohort could, on average, face a reduction of $355, $872, and $1,408 in yearly earnings depending on the scenario. In present value terms, this amounts to between $6,472 and $25,680 dollars in lost earnings over a typical student’s lifetime. As closures continue in low- and middle-income countries, the pessimistic scenario is more likely. Exclusion and inequality will likely be exacerbated if already marginalized and vulnerable groups, like girls, ethnic minorities, and persons with disabilities, are more adversely affected by the school closures. Globally, a school shutdown of 5 months could generate learning losses that have a present value of $10 trillion. By this measure, the world could stand to lose as much as 16% of the investments that governments make in this cohort of students’ basic education. Without drastic remedial action, the world could thus face a substantial setback to the goal of halving the percentage of learning poor — and be unable to meet the goal by 2030. The findings underscore the need for swift policy responses to offset the learning losses resulting from the pandemic and accelerate learning by building more equitable and resilient post-COVID education systems, that enable children to learn continuously both in schools and at home.