The project “Functional Writing in Primary School” (FUS) aims to increase the quality of the teaching and learning of writing in the first years of schooling. The primary aim of the project is to investigate what effects an early start with functional writing might have on students’ ability to use writing as a tool for learning and communication within school subjects. Such an approach will be novel as it already from school year 1 combines writing for a variety of purposes in meaningful ways with learning of alphabetic codes. The main part of the FUS project will be organized as an experimental intervention project revolving around teachers’ professional learning and students’ classroom actions in writing instruction in school years 1 and 2. The expected outcomes of the project are evidence-based knowledge of effective writing instruction for young learners and descriptors of expected trajectories of writing development.