Accountability pressures and the Common Core State Standards for Mathematics have created complex demands for educators, especially early-career teachers (ECTs). Analyzing longitudinal data, including the social networks of 119 ECTs, we find that ECTs increase their ambitious mathematics instruction when their network members positively interpret accountability pressures and curricular standards as manifest in standardized tests and evaluation. This estimated effect is net of an ECT's rich covariates, including the levels of ambitious mathematics instruction at the beginning of the academic year. It is implied that not all ECTs experience accountability pressures and curricular standards in the same way--their experiences are affected by the immediate networks in which they are embedded. Corresponding guidance for teacher educators and administrators is given.