Districts are increasingly making personnel decisions based on teachers' impact on student-achievement gains and classroom observations. In some schools, however, a teacher's practices and their students' achievement may reflect not just individual but collaborative efforts. In other settings, teachers' instruction benefits less from the insights and support of their colleagues. This article analyzes multiple measures of teacher and teaching quality for 24 language arts teachers in New York City who teach in different types of school environments. Teachers in different value-added quartiles were observed and scored using two protocols, PLATO and CLASS. Schools were categorized as more and less functional using Department of Education environment grades. To compare the practices of higher and lower value-added teachers in more and less functional schools, we conduct MANOVAs of observation scores and use qualitative coding of field notes. We find value-added measures and observation protocols provide confirmatory information in less functional schools but provide contradictory information about teacher quality in more functional schools. Implications for teacher education, policy, and future research are discussed.