This research situates within the framework of the paradigm of New Childhood Studies which acknowledge agency to children, thus becoming social actors that can also build their own cultures and influence adults' ones. Under this perspective children are seen as talented and skilled negotiators in relationships both with peers and adults, having voice to shape and modify the space they live in. The aim of the research is to study the formation of children's cultures in the processes of reproduction, internalization and interpretation of religious practices, with a special attention to reveal the form and content of agency. The research question was organized around three topics. The fist one aims to understand how children structure peer cultures within the context of religious practice. The second focuses on forms and contents of the negotiations that children engage with adults as regards of participation in the catechism and content of activities and finally of attendance at Sunday Masses. Furthermore, it investigates on what are children's request, how they express their needs, to whom children present them and what kind of relationships do children have with adults. Finally, the third focus is centered on interpretative reproduction and in particular on meanings and senses that children attribute to the catechism they attend. Therefore this research has focused in particular children's experiences during the final year of their preparation course of first communion, observing both the whole year of catechism and the ceremony in which they receive their first eucharist. The three focuses are bound to each other by trying to identify how gender and social class of children affect the different representations emerging. Research design was meant to combine together different methods, outlining various stages that allow us to switch from moments of research and analysis to space of reflection, useful to edit and re-calibrate ongoing approach in the field. The multi-method approach made possible to combine qualitative approaches such as ethnographic observation and focus groups, and quantitative approach as the sample survey. As for participant observation, it was decided to focus on children's experiences attending courses in preparation for their first communion in two different Catholic parishes of the city of Mestre (Venice). These two have been identified on the basis of a religiosity criterion along a continuum that ranges from a maximum of religious homogeneity to a maximum of religious non-homogeneity. Concerning the first case, it was involved a parish located in high quarters with a majority of Catholics, mostly Italians, for the second one it was identified a parish in a neighborhood where there are also other religions and nationalities. We conducted in both cases a twenty hour observation, for a total amount of forty hours. We also held four meetings in which children were asked to participate in focus groups. These were structured and presented to children as laboratories in which they would discuss together what they do at catechism. Moreover they had the opportunity to contribute along with the researcher to review the sample survey. Finally, we made a sample survey using a questionnaire that would allow us to describe with a large sample children's perceptions, thoughts and opinions on the catechism, their first communion, confession and in general on the religious practice world to which, more or less voluntarily belong. The survey was carried out in ten parishes of Mestre and Marghera and six parishes in Bassano del Grappa and its surroundings, for a total of sixteen parishes and 430 questionnaires collected. Thus, research has shown two results. The first concerns the ways in which children express their agency in catechism shaping their relationships with their catechists and allowing children a certain freedom of action. In this way the structure of the catechism depends on children's agency, and in particular on their ability to change it through sabotage and negotiation mechanisms that determine variations in the structure of activity. Finally, the second result concerns the process of individualization of belief which is evident already in children who are preparing for their first communion. In particular, it becomes evident in several episodes in which children have reinterpreted the traditions of Christian rituals, in the way of considering the sacraments, in the way they pray, their commitment to Christian values and beliefs and lastly questioning and doubting some mysteries of the Gospel they heard Therefore, while children up to now found only a marginal role on sociology of religion and they were seen especially through adults referring children experiences, this research aim to add a space for children and childhood on the reflection in studies of religious practices.