How can a bonus program affect the performance of teachers in classrooms? This paper collected data from teachers employed in Brazilian state-run schools to examine the key mechanisms through which a teacher bonus scheme can have a causal effect on the academic achievements of students. Using mixed-methods research and data triangulation from questionnaires and semi-structured interviews with teachers, this study finds limited empirical evidence supporting the bonus program of the state of São Paulo. The bonus program created no additional incentive for educators to start/continue working in state schools, and it was not responsible for the improvement of teaching activities.