Abstract This study was designed to determine the effects of teacher leadership on student achievement in middle school math and science. Participants were 173 8th grade students, and eight teachers — four of whom were identifed as teacher leaders. The experimental groups were comprised of students who were instructed by teachers identifed as teacher leaders; and the control groups were comprised of students instructed by teachers not identifed as teacher leaders. Each experimental and control group was compared using the Explorer test results to determine equivalence between groups. An ANOVA performed on End of Quarter Test data in advanced and non-advanced math and science revealed a signifcant difference in both the advanced science and math groups; teacher leaders are positively correlated with higher scores of the advanced math and science groups. 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