This paper aims to analyze the form that takes the writing assessment in two campaigns that explore students learning at the end of primary education, which corresponds to the sixth year. We are referring to the Third Regional Comparative Study (UNESCO, 2015), organized by the Latin American Laboratory for Assessment of the Quality of Education (LLECE-UNESCO) and the National Campaign for Evaluation (ONE) conducted in 2013 by the National Directorate for Information and Assessment of the Quality of Education (DiNIECE, 2014) in Argentina. Additionally, it takes up theoretical contributions derived from research on the processes involved in writing and presents the main results obtained by the subjects examined in the two aforementioned studies, considering some central aspects of the curricular designs for this level in the reference country. This is relevant as the TERCE starts from the curricular analysis of the participating countries. It should be noted that the investigation about writing has been belatedly incorporated to the educational quality assessment programs, mainly due to the difficulty of analyzing textual productions in large-scale approaches. However, it is a core skill within the conceptual framework of "life skills" (Atorresi, 2005).