To what extent does school-based management (SBM) influence teachers' commitment? Using a longitudinal research design, this study reveals that SBM positively affects teachers' commitment to the teaching profession and to students' academic achievements and negatively affects their commitment to the school and to students' social well being. At the same time the findings show that teachers' autonomy on the job remained unchanged after SBM was introduced in schools. It is argued that SBM is perceived by teachers as a potential to increase their professional autonomy. However, based on the assumptions of the exchange perspective, the findings show that teachers increase their commitment towards issues that potentially may benefit them most. The study concludes that more time is needed before the impact of SBM on teacher commitment may be fully understood. However, it is argued that high demands for teacher effectiveness have to be followed by sufficient benefits and professional autonomy if SBM is to promote commitment rather than teacher burnout.