Purpose: Studies demonstrate the central role of principals in developing and sustaining teacher commitment to their school. Teachers' commitment to their school impacts teaching, learning, innovation and school climate and manifests job satisfaction. Commitment strongly relates to teacher attrition. Attrition is important in the study of school success and failure given its strong predictive link to student learning. Design/methodology/approach: This study thus identifies relational practices of principals who successfully develop and maintain high levels of commitment among their teaching staff compared to those principals who fail to maintain high commitment or fail to raise low commitment among their teachers during the school year. To investigate this process, this study uses longitudinal, within-year school network and climate data for teachers and principals in 15 American charter schools. With these data and theories offered by social-psychology and organizational studies, the interpersonal leadership and school climate conditions set forth by the principal link to the fluctuating levels of commitment among teachers. Findings: Despite the consistently established link between employee commitment and organizational success and failure, this operationalization of changing levels of staff commitment is a novel contribution to the discussion of organizational principal leadership failure. This study clearly tests the questions: Which emotional responses prove volatile to teachers' repeated exchanges with their principals? How do principals' relational practices impact teachers' commitment to teaching? Among the strongest findings is the key practice of principals to maintain trust--interpersonal and schoolwide--to improve commitment among teachers and avoid loss of commitment by the end of the school year. Practical implications: Relational practices of principals can promote quality relationships that uphold trust and sustain environments conducive to maintaining high organizational commitment. When leaders fail to establish and maintain quality relationships, challenges experienced during a school year become more difficult to overcome. Originality/value: The opportunity arises to test the time-varying aspect of interpersonal relations in organizations and the subsequent idea about how organizational leaders maintain strong relationships, strengthen poor ones or repair injured relationships. These results evidence teacher commitment is prone to decline at the end of the school year yet the chance and magnitude of the fluctuation directly responds to changes in principals' relational practices. With relational practices, principals can induce affective responses from teachers at the interpersonal and organizational level that improve commitment among teachers and reduce drops in commitment.