Improving preservice teachers' argumentative competence is a social and educational imperative. This study focuses on the contribution of a sequence of learning tasks, designed as epistemic practices and following a learning progression approach, to enhancing student teachers' scientific argumentative writing. The participants were 47 preservice primary teachers who enrolled in a Developmental Psychology course, and one lecturer. Preservice teachers progressively acquired the vast majority of aspects involved in scientific argumentative writing. The most important difficulties experienced by the preservice teachers revolved around intertextuality and the creation of theses. Key conclusions on this teacher education experience are presented in the final section of the paper.