This study investigated the effectiveness of collaboration between college lecturers and student peers in assessing the instructional practice of in-service student teachers (ISTs). The study was inspired by criticisms that college lecturers’ assessments were not producing valid critiques of ISTs’ mathematical and pedagogical competencies to implement strategies they learned in their coursework. Case studies of two pairs of ISTs, one pair at a state high school and the other at a private high school, provided data for this study. During their coursework, ISTs learned new pedagogical skills and upgraded their content knowledge. Findings indicate that lecturer and peer assessment of the same lesson taught by an IST resulted in different but complementary critiques. The lecturer’s critique highlighted both strengths and weaknesses of a lesson while the peer’s critique refrained from pointing out weaknesses of a lesson. An important implication for the findings, in Zimbabwe, is that the deployment of ISTs in pairs for teaching practice may be beneficial to their professional development.