For the first time in history, nearly every child has a chance to go to school, no matter where they are born or how wealthy their family. On the face of it, global efforts to educate the world have been a huge success. But although classrooms are brimming with children, the students are, more often than not, struggling to learn. Even basic literacy—arguably the fundamental skill acquired in school—is elusive for many students. In India, half of fifth graders cannot read a simple story. In Uganda and Mali, only one in fifty second graders can read. Tests administered internationally reveal that the average learner in a developing country performs at the level of the worst performers in countries like the U.S.