In this meta-analysis study, different leadership approaches were combined, and the relationship between educational leadership and student achievement was analyzed. In the literature review, 151 research articles/dissertations, independent from one another, were brought together, and 131,498 study subjects were included in the sample group. The results of the analyses performed with a random effects model revealed that educational leadership has a medium-level effect on students' achievement. Educational leadership has comprehensive effect on student achievement in vertical-collectivist cultures (e.g., in Asian) than horizontal-individualistic cultures (e.g., in USA). As was expected, the most comprehensive effect among leadership theories was found in instructional leadership. Considering the effect of educational leadership on students' achievement, it is recommended to examine the effect of leadership on other components of school and stakeholders in future studies.