Brazil has been experimenting change in their religious field with the decrease of catholicism and increase of protestant religions, especially those of pentecostal denomination, and individuals declared without religion. It is attested that society is living a process of moral reform and the public school is one of the main stages. Such institution is also, to a high degree, the result of intense social dispute. This situation is the focus of this dissertation. It is developed, under the concepts of secularization and laicity in order to understand the Brazilian process, towards the constitution of a pluralist society. It is noticed historically: through empiric clues and bibliography; also, through legislatives propositions and recent public policies. It is noted that the interface between religion and school in Brazil is intrinsic, sometimes showing explicitly, sometimes subjacent to disputes for the constitution of what is comprehended as public school. The innovation is the transition to a more diverse religious field, especially because of pentecostalism shaking the complacent situation between State and Catholic Church, thus disputing the meaning of the concept of laicity or, ultimately, that of democracy in the daily relations waged at the schools floor.