Argumentative writing tasks that foster logical reasoning skills are the basis for ethical participation in a literate society. They are also valued intellectual tools that acquire special importance in the construction of knowledge and the regulation of thought. The purpose of this study is to analyze the development of argumentative writing of elementary school students in Chile whose teachers participated in a professional development program (PDP) based on a teaching/learning model centered on communicative problem solving through writing. Using a quasi-experimental mixed method, the argumentative writings of 238 students (experimental group= 124; comparison group= 114) were evaluated using a pre- and post-implementation test of the PDP through a rubric based on: (a) the autonomy of the written text; (b) discursive aspects; and (c) normative aspects. The results show that students in the experimental group performed better on the autonomy and discursive aspects of their final written assignments than their peers in the comparison group.