The teaching of English as a Foreign Language to Children as well as its research are in expansion not only in Brazil but all over the world (Cameron, 2003; Gimenez 2010). Among the studies in the area of teaching English as a Foreign Language to children there is a lack of researches that evaluate and analyze data that come from interventions in the teaching of writing to literate children aged between 8 and 10 (Figueira, 2010). With the objective of contributing to the Teaching of Writing in English as a Foreign Language to Elementary School Children, this dissertation aims to demonstrate a) how a pedagogical intervention, that was held at a private school in São Paulo, taught the persuasive text and b) to discuss the implications of this teaching to the participants were. In this master research, the researcher and teacher aimed to intervene in the students' comprehension of opinion writing in order to provoke the expansion of students' comprehension (Daniels, 2011; Magalhães, 2009), as well as to promote their writing improvement. In conformity with Davydov´s learning actions (1988), students answered the problem-question elaborated for the course, formulated representations about the characteristics of persuasion, analyzed biographical and persuasive texts and, in the end of the intervention, wrote persuasive texts about the real inventor of the airplane. The pedagogical intervention had its basis on the Cultural Historical Activity Theory, in conformity with the theories of Vygotsky (2007) and Davydov (1988). For Vygotsky, the intellectual functions of human beings are not mere results of biological maturation, as if they were something natural and innate for all human beings. Instead, the intellectual functions are socially constructed with the fundamental assistance of language. This reveals that higher mental functions derive from social interaction, from social and historical practices. In this sense, cognition emerges not only from biological functioning, but also from the integration of biological and social practice (Vygotsky, 2007). Another theoretical basis used for the intervention was the Australian School of Genre. In this perspective, the textual genre is materialized through language, which is a means through which human beings make meanings in social contexts (Eggins, 2004; Halliday & Matthiessen, 1994; Martin, 2008). In this way, genre can be seen as a tool to build Zone of Proximal Development and expand students' knowledge. These goals are connected with the theoretical perspectives adopted since their objective is to promote agency in the field they act upon (Lantolf, 2000, 2007; Spinoza, 1998; Vygotsky, 2007). Analysis of data revealed that the intervention promoted awareness of students in relation to the persuasive function of opinion texts. Moreover, the data analysis showed that students improved their opinion writing in relation to the pre-tests realized before the pedagogical intervention. The conclusion remarks that there is still much to do in the area of writing as a foreign lan...