We developed the integrated model of teacher's attention to examine teachers' a) situation awareness of the overall classroom and b) professional vision of individual pupils. Using mobile eye tracking in real classrooms, we analyzed teachers' eye movements using a novel metric, the Gaze Relational Index. The findings indicated that situation awareness involves shorter and more frequent gazes, while professional vision requires fewer but longer gazes. Experienced teachers showed faster and more varying visual attention compared to student teachers. This study provides valuable insights into visual processing in real-life classrooms, addressing the gap left by previous studies.