The psychological environment of schools is a powerful determinant of staff well-being and educational outcomes for children. The work reported here explored teachers' Collective-Efficacy (CE) and well-being. Staff in a sample of schools completed a survey of their CE. A sub-sample of teachers was interviewed to elicit views about the relationship between CE and leadership practices. Overall staff CE was correlated with key indicators of pupils' attainments. Four themes in the interviews indicated attributions for staff well-being and motivation: Communication, Learning, Supporting Roles, and Stress Management. Enhancing CE is critical for staff well-being. At a time when staff recruitment, retention and well-being may be jeopardised, the findings here indicate the critical importance of professional relationships for the ethos and effectiveness of schools.