In recent years, several studies have found that informing primary schools of their students’ achievement leads to changes in school management, instruction, and learning. We conducted an experiment in Salta, Argentina to understand whether school systems should go one step further and support principals to act on the information they receive. We randomly assigned 100 public primary schools to: a diagnostic-feedback group, in which we administered math and reading tests and made results available to principals; or a performance-management group, in which we also provided principals with training and an online dashboard to develop, implement, and monitor school-improvement plans. The intervention had limited impact on students’ performance in school during the study, but in the two years after it concluded, it reduced repetition rates in all target grades and it increased passing rates (reduced failure rates) for cohorts with two years of exposure. In fact, when we compare the schools in our study to other urban and semi-urban schools, they have lower dropout rates both during and after the study across all target grades. Our study suggests that school-management practices take a longer time to change than typically expected and highlight the importance of tracking post-intervention outcomes.