This study investigates the influence of structural transitions to high school on adolescents' friendship networks and academic grades from 6th through 12th grade, in a direct comparison of students who do and do not transition. We utilize data from 14,462 youth in 51 networks from 26 districts (Promoting School-Community Partnerships to Enhance Resilience). Results underscore the challenging nature of compulsory school changes. Students that structurally transition to high school between eighth and ninth grade, as compared with those who do not, receive fewer friendship nominations following the move and are more likely to become isolates, according to a three-level Poisson model. Students who transition also report significantly lower odds of obtaining high grades after the shift, and these penalties persist throughout high school. Our findings highlight the social and academic difficulties associated with this particular normative adolescent life transition and point to a disruption in social network ties as part of the problem.