The primary aim of this theoretical and methodological paper is to conceptualise early school writing instruction (with 6 and 7-year-old students) through a critical discourse analytical (CDA; Fairclough, 2003) perspective. By drawing on empirical examples from two L1 classrooms, the paper provides an example of how a CDA analysis may be operationalised, particularly in an educational setting in primary school years. In doing so, the paper unveils how social power permeates the discourse practices of early school writing and how its effects on writing instruction may be understood. The data consists of video-recorded observations of writing instruction in two classrooms and transcribed semi-structured interviews with two teachers. The conceptualisation shows major differences in the effects of power in discourse in the two classrooms, shaping the discourse practice in various ways. It furthermore becomes evident that these classrooms are sites of power struggles with effects on discourse and where discourse practices, in various ways, (re)construe both the social world of the classroom as well as what is being taught. However, rather than reproducing social power structures per se, this paper suggests that the classroom holds potential for contestation and transformation of structural power, not least dependent on the actions of the teacher.