Purpose: Principal instructional leadership and teacher participation in decision-making are conceptualized as shared instructional leadership (SIL) -- a management philosophy that positively impacts student academic performance. However, the statistically meaningful relationship between SIL and student performance remains controversial as SIL functioning is influenced by various fundamental school conditions shaped by education policy, including high-stakes accountability, school autonomy and teacher professionalization. The authors examined the relationship between three SIL policy configurations and promising student performance: inclusion, exclusion and insensitive to SIL. Design/methodology/approach: The authors used fuzzy-set qualitative comparative analysis on data obtained from the Program for International Student Assessment (2015) results, including principals' responses to leadership questions and school conditions shaped by policy, and student science scores in 64 countries and areas. Findings: The role of SIL in student performance varied among the three configurations, and the condition of teacher professionalization in the configuration was consistently associated with high student performance. Originality/value: SIL can create conditions for continued professional development of the teaching workforce in conjunction with school conditions shaped by policy.