Abstract This study investigates three primary school teachers’ experiences of working with formative assessment intended to develop pupils’ writing development. The study applies a sociocultural perspective to examine how teachers in grades 1–2 reason about their use of formative assessment to develop pupils’ writing. The study seeks to ascertain how the teachers reason about pupils’ texts in relation to the text triangle. The results of the study show that the teachers, in their work with formative assessment and writing development, proceed from set goals for the term which apply to all the pupils in that year. The teachers make the pupils aware of these goals by returning to them several times during the term. The intention is to remind the pupils of the goals. The three teachers also work with individual goals for the pupils via the pupils’ individual development plans. The informants all reason in much the same way about formative assessment in writing instruction in relation to the text triangle. The teachers consider that they work with the different qualities shown in the different levels of the text triangle, based on the pupils’ prior knowledge and experience of writing.