The development of professional competence of school managers in terms of the implementation of state tasks is the key-point and condition for achieving national and strategic development goals in the field of education, i. e. the entry of the Russian Federation into the top 10 countries in the world in terms of the quality of general education. Since the traditional form of professional development does not fully take into account the formed targeted requests in terms of the content of professional development, and requires an individual approach to their resolution, there is a need to modernize the system of professional development and to organize the managerial mentoring using mentoring technology as "horizontal training". The difficulty of using mentoring as a learning technology lies in the deficit of knowledge content of this phenomenon, and its insufficient use in the education spaces. Based on the critical study of current scientific scholarship, the article identifies the key differences between mentoring as a learning technology and у coaching, mentoring, and consulting. The presented structure of the mentoring session in the format of a professional developing conversation allows us to understand thoroughly the content of mentoring managers of educational organizations, as well as to identify the key-competencies which are necessary to use in the activities of a senior btf employee as a mentor. The results of the study expand the knowledge about the phenomenon of "mentoring" in the education allowing us to determine a mechanism for mentoring managers to develop their professional competencies. Keywords: managers; mentoring; mentor; mentee; criteria; competencies; training technology.