In this article, we present findings from a three-year comparative longitudinal and ethnographic study of how schools in two cities, Buffalo and Denver, have taken up STEM education reform, including the idea of "inclusive STEM-focused schools," to address weaknesses in urban high schools with majority low-income and minority students. Although introduced with great fanfare, the data indicate that well-meaning efforts toward expanding opportunities in STEM-focused schools for low-income underrepresented minorities quickly dissolved. We focus on mechanisms that seem to underlie this dissolution and consider its contributions to short- and long-term inequalities.