This article aims at providing some guidelines about the development of argument skills among 5 year-old Argentine children. Our main objective in principle is to establish that 5 year-old children can have a critical discussion with their peers, and to state that, as a consequence, their arguments can be assessed by examining (some of the major) informal fallacies proposed by Walton (2008). The corpus of analysis for this paper corresponds to a conscientious selection of some (significant) fragments from another corpus (Molina, 2010). All the dialogues were part of bigger dialogues. The context of all of them is the same: interaction among peers during an art class in a public elementary school of the south of Tucumán (Argentina). The children are 5 years old. From the analysis of the corpus, we claim that these young children are able to take part in persuasion dialogues (critical discussions) with their peers. As a result of that, we want to prove that the arguments advanced in those critical discussions consisted of, more often than not, valid arguments at a logical level. In this case, our theoretical framework will be the informal logical approach to argumentation (Walton, 2008; Tindale, 2007).