The article starts with a brief presentation of the history of school psychology in the world and in the Czech Republic. It shows that in the past the profession of a specialist within the school was equally put across with difficulties in other countries and that it faced resentment and fears of other actors of the system. The author starts with the idea that a school psychologist is a significant element in the relational network of the school institution. His substantial difference lies in his working with the entire system of the school - not only with its isolated members who have already become part of a problem. Furthermore, she shows where critical points in the professional activity of a school psychologist lie and what are the consequent demands on him/her in different relationships within the system: in the relationship to the director/headmaster (difficulties with the overlap of the expert - non-expert and subordinate - superior relationships), to the educational staff on the whole, to individual teachers (e.g. the demands on the role of a mediator between a teacher and pupils or a teacher and parents), to a school-class on the whole, to an individual pupil (a sensitive issue of producing and maintaining mutual trust) and to parents. Finally, the article deals with the differences in the work of a school psychologist within the school and in counselling institutions.