There are more children in school worldwide today than at any other time in history, pandemic-related disruptions notwithstanding. In 2010, the average adult had completed 7.6 years of school, more than double the 3.2 years completed by the average adult in 1950. Development experts have long argued that an expansion in school enrollments would equip the next generation with knowledge and skills to enhance their economies and promote a better quality of life. But a new database of detailed student-achievement data suggests that greater school enrollments have been followed by little to no growth in learning in most parts of the world. The authors constructed the Harmonized Learning Outcomes database by linking regional assessments of core academic subjects in less-developed countries to international achievement tests commonly administered in the wealthier parts of the world. This database of 164 countries allows the comparison of student performance in regions that are typically excluded from international comparisons, such as sub-Saharan Africa and Latin America, to that of more affluent students in Europe and North America. The data cover 98 percent of the global population and track student-learning outcomes from 2000 to 2017. The authors find that while rates of school enrollment topped 90 percent in every region by 2010, learning outcomes are low and have barely budged over the past couple decades. In North America, where school enrollment rates have been high for decades, the database shows that student performance on standardized tests in reading, math, and science barely budged between 2000 and 2015. Meanwhile, countries that have made dramatic progress in achieving high rates of schooling, such as Brazil and Ghana, still have very low rates of student learning. Expansion in access to school may provide more opportunities to learn and may have other benefits as well, but schooling does not guarantee learning, and the relationship is not one to one. To understand the potential benefits of the global growth of education to economies around the world, we cannot assume that schooling leads to learning. Measuring learning directly is essential.