Using a unique longitudinal dataset collected from primary school students in Pakistan, we document four new facts about learning in low-income countries. First, children’s test scores increase by 1.19 SD between Grades 3 and 6. Second, going to school is associated with greater learning. Children who dropout have the same test score gains prior to dropping out as those who do not but experience no improvements after dropping out. Third, there is significant variation in test score gains across students, but test scores converge over the primary schooling years. Students with initially low test scores gain more than those with initially high scores, even after accounting for mean reversion. Fourth, conditional on past test scores, household characteristics explain little of the variation in learning. In order to reconcile our findings with the literature, we introduce the concept of “fragile learning,” where progression may be followed by stagnation or reversals. We discuss the implications of these results for several ongoing debates in the literature on education from Low- and Middle-Income Countries (LMICs).