This study had two objectives. One objective was to assess the psychometric properties of a survey instrument measuring a new latent variable, Academic Culture (AC), combining three observed variables academic press, disciplinary climate and teachers' uses of instructional time. The second objective was to replicate the results of an earlier study identifying AC as a significant mediator of school leadership's influence on student learning. Data for the study were provided from 2068 teachers located in 49 schools in 14 Texas school districts, as well as student achievement data from the State of Texas Assessments of Academic Readiness (STAAR) and student socioeconomic (SES) data available from school websites. Second order Confirmatory Factor Analysis (CFA) and Many-Facet Rasch (MFR) models were used to examine the survey instrument's construct validity and its measurement invariance. Structural Equation Modeling was used to identify the extent to which AC mediated the effects of school leadership on student achievement controlling for student SES. Rasch analysis and CFA confirmed the measurement invariance and several forms of validity of the survey instrument. Replicating the results of an earlier study, results of structural equation modeling demonstrated significant effects of AC on student achievement and identified AC as a significant mediator of school leadership effects on student achievement. The study contributes to the quality of instruments available to school leaders for their school improvement work and to researchers inquiring about the most promising variables mediating the indirect effects of school leadership on student success.