In the school context, feelings and emotions are generally perceived as obstacles to learning. Today, however, the introduction of complex real-world issues in lessons of Geography, History or civic education, such as international migration or cultural diversity, blurs the classic boundaries between emotions and cognition when they prompt students' personal opinions and experiences. In the frame of a research on teaching and learning practices in education for cultural diversity, this paper examines how students' personal emotions were elicited in the lessons, and how they were semiotized, transformed in the course of social interactions. We analyze empirical data gathered in 12 Primary and Junior school classrooms in Switzerland. 12 teachers and 232 students (from 11 to 16 years old) participated. We adopt a cultural-historical perspective inspired by Vygotsky and his followers and show the interactional processes by which the emotions undergo semiotization and influence the unfolding of the students' psychological processes. In the sequences we analyze, using the Valsiner's schema (Human Development, 44, 84–97, 2001), we identify three different modalities of semiotization: 1) the students' feelings are simply verbalized and linked to the speaker's affective world; 2) the verbalized emotions are reframed and interwoven with factual information; 3) the verbalized emotions are linked to information and reframed with collective emotional experiences. These processes are described, illustrated and discussed. We shed light on the central role of the verbal interventions of the teacher (who supports but also hinders the processes sometimes) and of materiality, here photographs, which mediated the teacher-student interactions.