To estimate the long-term effects of the Reading Recovery® intervention, a regression discontinuity design (RD) was implemented in a randomly selected sample of Reading Recovery schools during each year of the federally-funded i3 Scale-Up external evaluation (2011–2015) and also in one additional cohort during the 2016–2017 school year. Long-term outcomes were measured by collecting scale scores on state achievement tests in reading or English language arts (ELA) that were administered to students during 3rd and 4th grades (2013–2019). We were able to record and link 3rd grade state test score data in reading/ELA for 9,879 students, and 4th grade state test data for 6,345 students. Results suggest that the long-term impact of Reading Recovery on students’ reading/ELA test scores in 3rd and 4th grades is statistically significant and substantially negative; students who participated in Reading Recovery in first grade had 3rd and 4th grade state test scores in reading/ELA that were, on average, .19 to .43 standard deviations (about one-half to one full grade level) below the state test scores of similar students who did not participate in Reading Recovery.