The rapid expansion of this type of international school has increased the need for a mobile teaching workforce. Traditionally, international schools have relied on the transnational mobility of Western Anglophone teachers. It is, however, neither possible nor appropriate to service dual-curriculum and bilingual schools by hiring predominantly English-speaking teachers. The growth in the new type of schools catering for the local middle-class students has caused the mobility of local-hire teachers who work alongside English-speaking ones. Consequently, these mixed-hire schools present a number of relational challenges for teachers and school leaders. Most of the teachers are neither prepared for new educational contexts nor for workplace conditions that these schools offer. Often these schools turn into ‘toxic environments’, contributing to low staff morale, lack of collaboration between international and local teachers, ghettoization, poor communication with parents and, ultimately, to the turn-over of school leaders and teacher attrition. This paper focuses on practice architectures of international schools that provide built material-semiotic spaces for international-hire and local-hire teachers to either reproduce or hybridise their understandings of teacher professionalism and professional identities. It uses the concept of affective atmospheres to explore relational tensions and their effects on the professional formation and learning of teachers and school leaders. Empirical data are drawn from case studies of schools located in the two major countries that offer international education. The data sets include interviews with school leaders, international and ‘local’ teachers, as well as site specific texts and photography. The analysis focuses on tensions experienced by teachers in these schools. In particular, the article investigates how the politics of micro-management, unexplained top-down decisions, workload demands, unequal pay, professional misrecognition and communication barriers serve as a stepping stone towards understanding the affective practice architectures of these schools. The affective atmosphere is generated in the relational space of teaching practice where teachers interact with others and the workplace environment. It therefore cannot be limited to individual perceptions but, instead, should be understood as intersubjective intensities in the professional learning and formation of transnational teachers. The article discusses the role of individual and collective teacher agency in changing practices and their affective architectures.