The purpose of this research is to analyse what being a mediator teacher means or is likely to mean in children education. This investigation is based on i) Vigotski's concept of semiotic mediation, ii) on the concept of signs developed by Bakhtin; iii) on the studies of early childhood Sociology, and, finally, iv) on the theoretical texts that approached the topic between the 1990s and the year 2000. Focusing mainly on the relationship among individuals, this study seeks to investigate the types of mediations which occur between adults and children in the school environment. The research was carried out with two different classes of four and five- year-old children pupils, respectively, in a state school of Early Childhood Education and Primary School, with the purpose of comprehending how children and adults perceive themselves and perceive their actions in that particular environment. The field work provided a broad understanding of the mediating signs existing in the relationship between children and adults, their recurrences and also the differences in the types of mediation that occur in the every-day interaction in each group. The mediations identified between the adults and the children in group A (fouryear- old children) and B (five-year-old children) are: the organising mediations; challenging mediations, encountered in inter personal communication with their peers; informative mediations, and instructive mediations which position the teachers as models to be immitated. As for the mediations occurring when adults and children are engaged in joint activity, it could be noticed that mediation was necessary in situations in which children often requested the adults as a support to appproach problems that they were not be able to solve by themselves. There was also the kind of mediation which could be found in the adults' speeches and attitudes, regardless of their presence. Finally, it could be seen that some mediations were beyond the adult model. Yet, in all these relations, the signs have proved to be crucial tools, in that they reveal important ideas and concepts that enable us to discuss and reflect on the school practices regarding small children.