Purpose: The purpose of this paper is to examine how school leaders use high-stakes teacher evaluation to improve and, if necessary, remove low-performing teachers in their schools. It explores how cognitive, relational and organizational factors play a role in shaping the way school leaders implement teacher evaluation. Design/methodology/approach: Using a database of in-depth interviews with 17 principals and assistant principals, this study uses cross-case comparisons to examine one district's efforts to improve the performance of low-performing teachers through evaluation. Findings: School leaders' framing of teacher performance and their efforts to improve instruction reveal the cognitive, relational and organizational aspects of working with low-performing teachers and, if necessary, pursuing removal. Notably, this study found that cognitive and relational factors were important in school leaders' teacher improvement efforts, but organizational factors were most salient when attempting to remove teachers. Research limitations/implications: Because evaluating and developing teachers has become such an important aspect of school leaders' day to day work, this study suggests that school leaders could benefit from more assistance from district personnel and that preparation programs should build in opportunities for aspiring leaders to learn more about their role as evaluators. Originality/value: The success or failure of teacher evaluation systems largely hinges on school leaders, yet there is scant research on how school leaders make decisions to develop and remove low-performing teachers. This study sheds light on the central role school leaders play in implementing high-stakes teacher evaluation.