In the context of educational reform and the implementation of the 2018 General Education Program, teaching activities at upper secondary schools require systematic and comprehensive changes to meet the demand for improving the quality of education at this level. This article presents core theoretical issues related to managing changes in teaching activities at upper secondary schools, such as key concepts concerning the research topic, the necessity of managing changes in teaching activities, and the content of managing changes in teaching activities. These theoretical foundations serve as a basis for practical studies and for proposing solutions to enhance the effectiveness of change management in teaching activities at upper secondary schools.