The article draws on a policy experiment, intended to develop guidelines and recommendations for teacher evaluation. A systematic review, used in the experiment, revealed that teacher evaluation fails to fulfill its formative intention, and is reduced to summative technicalities when systems violate acknowledged principles from evaluation research. Interestingly, researchers rarely asked who were responsible for failed teacher evaluation attempts. Therefore, to better understand the relationship between school leaders and teacher evaluation, relevant studies in the systematic review were reanalyzed and more recent studies identified in a supplementary search. In total, 73 studies were examined and guided by the research question: What characterizes school leaders' activities in teacher evaluation? Fifteen of the studies included for in-depth analysis. The analysis revealed that how school leaders perceive teacher evaluation affects how they approach it. While some school leaders think as administrators, others identify with the profession. Policy assumptions, leadership and teacher professional learning are discussed, and the potential of professional learning communities (PLCs) to develop formative evaluation practices was analyzed. In the conclusion, it is argued that school leaders and teachers need a joint knowledge base for professional development and that with proper leadership, inquiry-based PLCs may strengthen the teaching profession.