This longitudinal study examined associations between changes in School Connectedness and changes in Affiliation With Deviant Peers among students from high-poverty backgrounds during the year immediately following the transition to middle school. Sixth-graders (N = 328) attending two middle schools in a large school district completed measures of School Connectedness and Affiliation With Deviant Peers at three points across the year. Results from parallel process modeling showed that students’ reports of School Support significantly declined across the school year, School Support and Affiliation With Deviant Peers were negatively associated at the beginning of the school year, and students who reported more declines in School Support were more likely to report growth in Affiliation With Deviant Peers across sixth grade. Gender differences were also found. Findings suggest that School Connectedness may be important for high-poverty students following the transition to middle school.