In 2023, ACER published the School Improvement Tool (SIT), the second iteration of the National School Improvement Tool (NSIT). A comprehensive review of international research was undertaken to inform the development of the SIT which consists of nine inter-related domains that describe the practices of highly effective schools and leaders. School leaders play a crucial role in facilitating and sustaining improvement. They influence a wide range of practices. These practices, when combined, have the potential to significantly improve student outcomes. However, leaders cannot achieve sustained improvement on their own. Staff who have an unshakable belief that every student can learn successfully, commit to meeting the individual needs of their learners through the effective implementation of curriculum, pedagogy, and assessment, and who are deeply committed to their professional growth, make a positive difference to student outcomes. This document provides a summary of research evidence that underpins each of the nine domains of the SIT. Acknowledging interdependencies between domains, it presents a narrative of key evidence and research-based considerations for each domain. Further detail about the evidence for each domain can be found in the School Improvement Tool Literature Review.