We use administrative panel data from seven states covering nearly 3 million students to document and explore variation in "academic mobility," a term we use to describe the extent to which students' ranks in the distribution of academic performance change during their public schooling careers. On average, we show that student ranks are highly persistent during elementary and secondary education--that is, academic mobility is limited in U.S. schools as a whole. Still, there is non-negligible variation in the degree of upward mobility across some student subgroups as well as individual school districts. On average, districts that exhibit the greatest upward academic mobility serve more socioeconomically advantaged populations and have higher value-added to student achievement.