The aim of this study is to describe and analyse the writing discourse in one classroom and how students learn through studying a topic, i.e. the teaching and learning of written argument. The study takes its stance from a sociocultural perspective and is influenced by discourse analyses, new literacy studies and critical literacy (Fairclough1989; Barton 2007; Janks 2010; Ivanič 2004). Data from year 6 in Sweden consists of observations, informal conversations, teachers’ planning and students’ written texts, i.e. letters to a newspaper editor. The results are presented in terms of four themes that became apparent during the reading of the data, viz. (1) teaching for learning - deconstruction; (2) dialogue and scaffolding for learning – enabling access; (3) reconstruction, feedback and students’ reflections for learning; and (4) writing to learn. The data is analysed and discussed on the basis of four concepts for developing critical literacy, viz. access, deconstruction, reconstruction and domination (cf. Janks 2010:21 – 32). The study indicates that explicit teaching of a written argument gives students access to the dominating structure of the genre if they are given the time and tools to reflect and be given feedback from the teacher.