Learning to write is a complex process and children have to orchestrate a range of processes and skills in order to produce written messages. Young children are facing increasing demands in terms of the expected complexity of their written messages in education settings across the world. Teachers, in turn, are challenged to support children and guide them towards independence in writing. This article explores the complexity of writing and, drawing on a study that describes the implementation of an observation as assessment framework for supporting writing, practical research-based strategies are provided to leverage observation as a form of assessment and how to support children to organise their own composition of messages.