Most science curricular reform efforts are designed by administrators or science education experts. It is less common for teachers to work collaboratively across disciplines to create, implement, and disseminate an integrated STEM curriculum developed for noncollege-bound students that ended up being popular across student populations at the school. The integrated Geometry in Construction curriculum was developed 12 years ago and has since been adopted by over 425 schools across the United States. This intrinsic case study describes the experiences and perceptions of two high school teachers (one in mathematics and one in industrial science/engineering) as they achieved agency to initiate a deep and sustained reform effort. Drawing on the theory of teacher agency, the factors motivating the teachers to enact their beliefs about students and teaching are described. As a result of increased professional agency (driven by professional discontentment, willingness to take risks, and encouragement by mentors), these two teachers (a) cogenerated integrated engineering-math curriculum with one another and their students and (b) addressed the needs of their community for affordable housing.