Аннотация
The changes in the contemporary world require teachers to develop new teaching approaches. These requirements can only be met with improvement in teachers’ professional training and assessment activities. Assessment activities are a key aspect of professional competence in the education process. Teachers and their students from the first gymnasium in Petropavlovsk participated in the study. The study employed a mixed-method approach over three years. The study aimed to answer seven research questions grounded in the literature by developing a training program and experimentally testing it among teachers. At the onset of the program, all teachers were at the critical (lowest) level for the formation of assessment activities. With consistent training and support, the teacher’s level of formation improved significantly, even to the optimal (highest) level. The study revealed four components of evaluation: motivational; informative; technological; and reflexive. These components were embedded in various criteria, indicators, and research methods. The study also revealed the questions commonly asked by teachers during the assessment and when engaged in student participation. This is the only study that has simultaneously examined teacher competence, interdisciplinary assessment methods, teacher development, and student cognition. The theoretical and practical implications of the study are discussed. Keywords: Assessment activity; assessment evaluation; pedagogical activity; teachers