Purpose: The purpose of this paper is to explore how effective school principals use systems thinking, aiming to present the systems school leadership (SSL) approach -- an approach where principals lead schools through the systems thinking concept and procedures. Design/methodology/approach: Participants were 28 Israeli school principals, selected as outstanding leaders by recommendations from their superintendents and according to their schools' achievements. The study employed semi-structured interviews as well as focus groups. Generating themes was an inductive process, grounded in the various perspectives articulated by participants. Findings: Data analysis generated four main characteristics of SSL: leading wholes; adopting a multidimensional view; influencing indirectly; and evaluating significance. Research limitations/implications: Further research that will explore to what extent and how often principals use systems thinking is required. In addition, replication in various educational contexts is important in order to substantiate the validity of the SSL's characteristics. Beyond principals' perceptions, more objective measures like direct observations are needed to evaluate actual implementation of SSL in diverse school settings. Practical implications: Identifying the SSL characteristics facilitates the development of practical processes for nurturing SSL in various stages of school leaders' educational career. Originality/value: This paper provides a useful conceptual and empirical framework to evaluate SSL as a managerial approach.