This paper presents and evaluates a teacher training approach called the cluster-based mentoring programme (CBMP) for the professional development of government primary school teachers in Pakistan. The study sought to find differences in the teaching practices between districts where the CBMP was used (intervention) and control districts where it was not used (non-intervention). Data were analysed to examine the effectiveness of the CBMP in terms of enhancing teacher practices and student behaviour. The paper differentiates those aspects of classroom teaching where the CBMP has been the most effective and where it has been marginally effective or not effective at all, thus leading to concrete policy lessons for teacher education programmes in Pakistan.