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. These estimates, based on the review of data from 164 countries around the world, appear to represent a substantial achievement toward human progress. In particular, they would seem to indicate the potential for dramatic economic growth in the developing world, which accounts for much of the enrollment difference. But does more schooling necessarily lead to economic progress? 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.