Summary: This mixed methods, convergent parallel design study utilized the Global Perspective Inventory and related open-ended questions to compare the responses of International Baccalaureate Diploma Programme teachers with their peers who teach the standard high school social studies curriculum, situated in three large public school districts in one Southeastern US state. The IB is considered one of the most important settings for effective K-12 global education, and it is important to determine the extent to which IB teachers demonstrate global competencies that differ from their non-IB peers. In general, teachers in both groups scored similarly, but the IB teachers scored slightly but significantly lower on inventory scales that measured their self-understandings in relation to their backgrounds and the extent to which they engage with people of diverse groups. However, when controlled for teachers' sociodemographic characteristics, IB teachers demonstrated higher scores on the inventory scale indicating their interactions with people of diverse groups. Furthermore, the differences between these groups was corroborated through teachers' qualitative responses to open-ended questions. Additionally, teachers' responses to open-ended questions demonstrated that teachers in both IB and non-IB groups who scored more highly on the quantitative inventory also generally had more detailed and nuanced global understandings. Moreover, teacher responses to open-ended questions highlighted barriers to global education, including curricular inflexibility, student tracking, and re-segregation. Teachers also reflected that their globally-focused professional learning has been most effective when it has been ongoing and has provided time for integration of learning into daily curricular and instructional planning.