Purpose: Decades of research on different leadership styles shows that effective school leadership is the degree of influence or synergy between teachers and principals around the core business of schools, instruction. While various styles, such as transformational, instructional, shared instructional, point to the similar measures of high organizational quality, the inconsistency in how these styles are defined and relate make it unclear how principals systematically improve schools. The paper aims to discuss these issues. Design/methodology/approach: This study used the 1999-2000 schools and staffing survey, n = 8,524 of US principals, since it includes a nationally representative sample of administrators who responded to a comprehensive set of leadership measures around a time of school restructuring reforms. Confirmatory factor analysis was used to identify different styles, and to measure the extent of their relationship. These factors were used to test a theory about why principals practice each of these styles to a different degree based on levels of shared instructional leadership. Findings: Based on the theoretical framework, principals should have a similar high influence over resources, safety and facilities regardless of degree of shared instructional leadership since these tasks address foundational school needs. However, principal and teacher influence over these resources differed across levels of shared instructional leadership more than principal-directed tasks of facilitating a mission, supervising instruction and building community. Originality/value: Differences in the practice of styles by shared instructional leadership did not fit changing, higher ordered needs as theorized instead seemed to vary by a hierarchy of control, the way in which principals shared influence with teachers.