Most integration programs transfer students between schools within districts. In this paper, we study Metco, a long-running desegregation program that sends mostly Black students out of the Boston public school district to attend schools in more affluent suburban districts. Metco increases the number of Black students in receiving districts dramatically. Because Metco students have substantially lower test scores than local students, this inflow generates a significant decline in scores, with an especially marked effect on the lower quantiles. This paper investigates the impact of Metco on receiving districts. Aggregate data on schools from districts throughout Massachusetts and micro data from a single large district strongly suggest the impact of Metco is largely a composition effect, since OLS estimates show no impact on average scores in samples of White or non-Metco students. On the other hand, OLS estimates using micro data show some evidence of an effect on the scores of minority 3rd graders in Reading and Language. Instrumental variables estimates for 3rd graders are imprecise but generally in line with OLS. Further analysis shows the negative effects on 3rd graders to be clearly present only for girls. Given the highly localized nature of these results, we conclude that any peer effects from Metco are modest and short-lived.