In recent years, the number of science, technology, engineering, and mathematics (STEM) specialized schools has been rapidly increasing internationally. In the United States, a new movement of establishing inclusive STEM high schools (ISHSs) aimed at expanding access to specialized STEM education for underrepresented and diverse student groups has begun to emerge. Due to its recent emergence, rigorous evidence on the impact of ISHSs on student outcomes is scarce and inconclusive. This study adds to this limited but growing body of empirical literature by examining whether ISHSs have an effect on student achievement, course-taking, and high school completion, and if effects vary by sociodemographic subgroups. Focusing on the Texas STEM academies--the largest cluster of ISHSs in the US, and analyzing a decade-long data from the Texas Statewide Longitudinal Data System, pooled regression analysis results showed that while ISHSs had no impact on student test scores in mathematics and science, the effects are positive on completing advanced level math courses in high school. Subgroup analyses indicated that ISHSs generally have no differential effects on student outcomes by sociodemographic subgroups, with the exception that they improve the rates of high school graduation for racial minority and low-income students.