The Center on School Turnaround (CST) has identified four levers, or domains, for dramatic change to rapidly improve schools: (1) turnaround leadership; (2) talent development; (3) instructional transformation; and (4) culture shift (CST, 2017). These levers are highly integrated -- the only way for each to succeed is to ensure that all four are enacted and aligned. Yet each requires an understanding of the unique knowledge, skills, and tools required for its enactment. This paper focuses on Domain 4, culture shift -- what it means, why it is essential for rapid improvement in a school, and -- critically -- how to move a school from a negative culture to a positive one that fosters student learning and success. A school's culture is a powerful force that will work for or against improvement efforts. A school with persistent and chronic low achievement has, almost by definition, spiraled into a negative culture that contributes to and is worsened by its failures. Rapid improvement, then, requires culture shift, an enterprise that requires changes in mindsets, norms, and attitudes and is as difficult and uncertain as it is essential. In this paper, the authors address the nature of that challenge. They define what they mean by school culture and differentiate between the school's culture and the variety of cultural influences students and teachers bring with them to the school. Throughout, the authors emphasize that the unrelenting focus of a successful school's culture is student instruction and learning. They address why, in particular, that means ensuring that everyday school and classroom practices substantively respond to, rather than ignore or simplistically acknowledge, students' home and family cultures. Finally, the authors offer steps schools can take to prepare for culture shift and a tool that can help launch and guide the change process.