Introduction. The article summarizes the results of the first year of work on the implementation of the scientific project "Evaluation of the effectiveness of the class teacher (including the development of performance criteria)" (730000F.99.1.BV10AA00006). The research is aimed at developing theoretical and methodological foundations for evaluating the effectiveness of the activities of class teachers in a modern school. The relevance of the task is determined by the significantly increased public attention in recent years to the organization of the educational activities of the school and the lack of unified, generally recognized criteria for evaluating the effectiveness of the key figure in the educational process of the school: the class teacher. Materials and Methods. The theoretical and methodological basis of the study is a set of methodological approaches: system-activity approach (V. V. Davydov, A. N. Leontiev, S. L. Rubinshtein, D. B. Edkonin); acmeological (G. M. Derkach, V. N. Maksimova); personality-oriented (E. V. Bondarevskaya, V. V. Serikov, I. S. Yakimanskaya); competence (A. V. Khutorskoy, I. A. Zimnyaya); criterion-level (I. A. Zimnyaya, N. B. Avalueva); task (V. I. Slobodchikov, G. A. Ignatieva); integrative, complex (A. P. Belyaeva). The following research methods were used: system analysis and synthesis, comparative and comparative, theoretical modeling, survey, method of expert assessments, study and generalization of pedagogical experience, methods of statistical processing of results. Results. The research team substantiated a structural-functional model for evaluating the effectiveness of the class teacher. On its basis, an integrative criterion matrix for evaluating the effectiveness of the class teacher was developed, including procedural, personal and productive blocks, each of which contains certain criteria and indicators. They are built taking into account the invariant areas of activity of the class teacher (activities for the education and socialization of the personality of the student, work with parents, with the class, with subject teachers, with social partners) and the corresponding analysis and evaluation technology. A method for evaluating the effectiveness of a class teacher's activity has been constructed as a way of a comprehensive diagnosis of his professional activity, the quality of interaction with all participants in educational relations and determining the degree of development of his professional and personal competencies. It includes an integrative criteria matrix, a class teacher's professiogram, procedural "packages", modern practice-oriented diagnostic tools. Practice-oriented tools of the assessment tool have been developed, which are part of the methodology, which provide objectivity, clarify the content of the assessment and significantly expand the possibilities for determining the effectiveness of the class teacher. These diagnostic tools are represented by checklists, graphic cases, questionnaires. The results of the study were tested, reviewed and discussed in seven constituent entities of the Russian Federation (St. Petersburg, Kaliningrad, Nizhny Novgorod, Moscow, Kirov, Ulyanovsk, Samara regions) online and offline in the context of determining their practical applicability. A positive response was received in the professional pedagogical community. Discussion and Conclusions. Theoretical and methodological foundations for assessing the effectiveness of class teachers have been developed on the basis of the above methodological approaches and a set of sound principles (openness, optimality and objectivity, consistency, criteria-based clarity, collegiality, a combination of expert assessment and self-assessment, etc.). The results of the study can be used in the mass practice of analyzing and evaluating the effectiveness of class teachers. In addition, they can be used in the professional training of future teachers at the undergraduate and graduate levels in the development of special courses on the organization of educational activities at school, as well as in the research work of graduate students studying the organization of educational activities of class teachers. The results of the study can be used in advanced training courses for teachers who perform the functions of class teachers, educational advisers, deputy directors of schools for educational work when designing additional professional educational programs on educational issues.