Thesis advisor: Larry H. Ludlow / In 2019, as in previous years, White students outperformed African American, Hispanic, and American Indian/Alaska Natives in a variety of K-12 outcomes (Darling-Hammond, 2007; de Brey et al., 2019; Jacob & Ludwig, 2008; National Education Association, 2015). The urgency of the opportunity/achievement gap is clear, as the current cohort of students under 5 years of age marks a turning point in student population demographics as the first in which 50 percent are part of a minority race or ethnic group (U.S. Census Bureau, 2015). Sociocultural integration (SCI) is included in the frameworks of successful bilingual programs (Howard et al., 2007; Scanlan & López, 2014). SCI considers the dynamics of relationships with oneself and others as being built in the context of one’s racial/ethnic, cultural, and linguistic background (Brisk, 2006; Feinauer & Howard, 2014). Acceptance and appreciation of cultural difference is critical for teachers (Bennett, 2003) and a number of pedagogical frameworks center teachers’ role of cultural brokerage as a pathway to fostering positive student outcomes (Grant & Sleeter, 2006; Suárez-Orozco & Suárez-Orozco, 2001; Villegas & Lucas, 2002). In this dissertation, I defined sociocultural integration in a teacher-centered way, and explicitly incorporate teachers’ racial/ethnic identity development in the evolution of their actions to support SCI. Second, I operationalized this definition and built a scale for measuring SCI using innovative “lived experiences” scenario items according to the Rasch/Guttman Scenario scale development methodology (Ludlow et al., 2020). The SCI Scale for Teachers showed desirable psychometric properties and is well suited to increase use due to ease of interpretability. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Lynch School of Education. / Discipline: Educational Research, Measurement and Evaluation.