This study examines the role of school leadership support in moderating the relationship between student socioeconomic status (SES) and academic achievement in mathematics and science at the 8th-grade level. Using data from the 2019 Trends in International Mathematics and Science Study (TIMSS) across 46 countries, meta-analytic regression models were employed to analyze country-specific results. While SES was found to have a significant positive impact on achievement in both subjects, school leadership support exhibited a negative and significant relationship with mathematics achievement and a negative but non-significant relationship with science achievement. Contrary to expectations, no significant moderating effect of school leadership support on SES-related achievement gaps was observed at the country-specific level. These findings highlight the variability in the influence of leadership practices across diverse educational contexts and underscore the challenges of leveraging leadership support to reduce inequities in achievement. The study emphasizes the need for further research into the contextual factors shaping leadership effectiveness, advocating for tailored approaches that address the unique sociocultural and educational dynamics of individual countries.