This paper describes the development and use of a tool designed to support educators to use a broad range of professional knowledge to enable inclusive literacy teaching that delivers social justice and narrows the attainment gap associated with poverty. The tool encourages teachers to formally recognise and act on a wide range of evidence about students as learners and to design their literacy curriculum and teaching according to this evidence. The research operationalised a Capabilities approach to inclusion and a design experiment methodology, working with 48 schools, 650 teachers and 12,783 students. A paired sample T-test showed a significant improvement in standardised age scores and that the 'tail of underachievement' shortened for all social groups. Goodman and Kruskal's gamma showed a weakening of the relationship between poverty and attainment. This gives cause for cautious optimism that attainment gaps associated with economic disadvantage can be narrowed if educators act on a wider range of evidence in literacy teaching, and if education researchers develop and trial tools to support them.