Inclusive science, technology, engineering, and mathematics (STEM) high schools (ISHSs), which combine nonselective admission policies with a STEM-emphasized curriculum and college-going culture, represent an emerging STEM-focused school model that has been rapidly expanding across the country. In 2006, Texas launched the Texas STEM (T-STEM) initiative, the largest investment in ISHSs in the nation, and opened the first seven T-STEM Academies. The number of T-STEM Academies has increased exponentially, reaching 55 in 2011 and 121 in 2016. Because of its recent emergence, rigorous evidence of the effectiveness of ISHSs is limited and the existing findings are mixed. This study adds to this growing literature on ISHSs by analyzing a decade-long data from Texas statewide longitudinal data system to assess the impact of T-STEM Academies on student achievement and educational attainment.