Book excerpt: Based on a DfES funded study of 300 teachers in 100 primary and secondary schools in England, the authors identify different patterns of influence and effect between groups of teachers, which provide powerful evidence of the complexities of teachers' work, lives, identity and commitment, in relation to their sense of agency, well-being, resilience and pupil attitudes and attainment. This, in turn, provides a clear message for teachers, teachers' associations, school leaders and policy makers internationally, in understanding and supporting the need to build and sustain school and classroom effectiveness.