The paper „The school educationist and professional teacher development through supervision” shows the results of a theoretical analysis and empirical research of the professional teacher development through supervision phenomenon. The theoretical part opens from the claim that continuous and quality professional teacher development is of importance for a modern school. Various studying and teaching models have been presented, along with their features (transmission, transaction, transformation). The key phenomenon dealt with in the paper is supervision as one of the most efficient methods of professional teacher development. The term, development, goal, participants, types and importance of supervision in general and supervision in school have been presented. The paper predominately deals with the role of the school educationist in teacher development through supervision. The term of pedagogical supervision has been defined and it has undergone analysis in the context of pedagogical supervision from the aspect of the school and class environment, subjective teacher theories and the peculiarities of teaching teachers as adult students. The role of the educationist in the cyclic process of pedagogical supervision has been analyzed: from planning and preparing, through supervising, to reflection and transformation of teaching. Based on the theoretical and empirical research, a model of professional teacher development through supervision has been given. In the empirical part of the research, the attitudes of teachers and school educationists of high schools in the Republic of Croatia to professional teacher development through supervision have been examined. A total of 822 teachers from 43 high schools and 73 educationists have been encompassed with the research. The attitudes of teachers and educationists have been examined in relation to these variables: sex, work experience, occupation, school type, occupational advancement and subject of teaching. Conclusions have been made based on the accumulated and processed data and the analysis conducted. In the research of teacher and school educationist attitudes to supervision as innovation, dimensions of supervision as a communication process, new role of teachers in supervision and the importance of supervision in school context have been examined. Based on the results obtained, it has been concluded that teachers and educationists give more importance to a supervisional approach to teaching, because it contributes to the quality of teaching and they benefit from it. The prerequisite for quality supervision of teaching is regular cooperation of teacher and educationist, as well as their communication based on trust and respect. With the supervisional approach to teaching, whose basic goal is the development of a teacher – reflexive practitioner, the educationist helps teachers in training them for this new role. Only a complete supervision can reach that goal, thus contributing to the development of the teacher as an individual and of the school as a system. It is very likely that the teacher will not perceive such supervision as a control of his or her work. Supervision of teaching can be one of the most efficient methods of professional teacher improvement, if it encourages learning and development of the teacher and the educationist, and if the educationist is helping teachers in planning their classes. Teachers will not accept supervision as long as it is connected with fear or if it is perceived as a control of their work. Researching the attitudes of teachers and school educationists to the activities of planning and preparing class visits, the dimensions of following factors have been examined: the subjects of planning and preparing classes, the setting of class supervision goals and the time organization of class supervision. The aforementioned parameters have been examined from the aspect of real situations (the existing state) and the aspect of the ideal situation (the desired state). It has been established that the majority of teachers and educationists thinks that, when it comes to planning and preparing class, the following is true: the educationist sometimes works with the teachers, which is the way it should be; the educationist helps the teachers when they ask for help and that’s the way it should be; the students are rarely involved, while they should be involved often; the goals of class visits are set together by the educationist and the teacher, which is the way it should be; the educationist always acquaints the teachers with the goal of class visits, before the visits themselves, which is the way it should be; the educationist never visits class unannounced, which is his or her right given he or she has a valid reason to do so; in our pedagogical practice the teacher and the educationist set the schedule of class visits together, which is the way it should be. Researching the attitudes of teachers and school educationists to the course of the teaching process, the dimensions of the content of class supervision and the quality of professional interactions have been examined. The aforementioned parameters have been examined from the aspects of real and ideal situations. It has been established that the majority of teachers and educationists states (real and ideal state) that: the educationist in the class most often monitors the student – teacher rapport, student activity and contribution to class; the class visits of the educationist have a beneficial influence on classroom teaching; the educationist seldom interferes in class without previous arrangement with the teacher. Furthermore, it has been established that educationists in most cases make their own class monitoring instruments, while they think they should be making them through coordinated efforts at professional councils. Based on the obtained results, it has been concluded that teachers and educationists give importance to all aspects of class monitoring. In the research of teachers and school educationists’ attitudes to the teaching process reflection, dimensions of the following factors have been examined: preparation of conversation after class, content of class reflection, quality of communication between teacher and educationist and time. Majority of teachers and educationists says (real and ideal state) that: they always sort out their notes and impressions directly after a class visit; the most frequent focus of reflection is the methodical aspect; following a class visit, the teacher and the educationist discuss the visit as equal conversation participants; the conversation on the class visit most often takes place immediately after the class; the date and time of the conversation is set by the teacher and educationist together. Moreover, it has been established that teachers, if needed, prepare for conversation with the educationist upon a class visit and that the educationist always talks with the teacher. Based on these results, it has been concluded that the teacher and educationist find all aspects of teaching important when it comes to reflection. In the research of teachers and school educationists’ attitudes to the transformational role of supervision, the following dimensions have been examined: supervisional learning and innovation in practice, supervisional learning and the increase of teacher competence, the presence of supervisional learning in practice and quality supervisional learning. It has been ascertained that the majority of teachers and educationists believe that: new possibilities of action can be found through conversation on the held classes with the educationist; supervisional learning brings changes in the teacher’s work; school educationist offers critical insight and enables seeing the class situation from a different perspective; supervisional learning contributes to the increase of personal and professional teacher potential; supervisional teacher development leads to a change in teaching practice and improvement of work quality; modern school requires more and more teachers researchers; supervisional development of teachers is sufficiently present in our pedagogical practice; quality supervisional learning includes innovation in classroom teaching; establishing the efficiency of supervision can be conducted through individual and group conversation. The results of this research point to positive teacher and educationist attitudes to supervisional approach of the educationist to teaching. They consider such an approach based on empirical learning, whose basic method is reflection of the practical experience with the goal of change and rise of work quality, contributes to the increase of teacher competence, teaching innovations and of the school’s quality of work.