This paper reports on a design-based intervention in urban primary and secondary schools serving culturally diverse students from low socio-economic status (SES) communities. The intervention capitalises on a partially implemented programme in seven schools which use digital devices (netbooks) and applications to raise literacy levels. Learning and teaching measures have been used to identify effective components which can be more systematically implemented. Classroom observations were employed to provide a profile of the use and quality of the literacy instruction and to identify effective instructional practices, thereby contributing to the redesign of instruction for cluster wide implementation. The study adds to a growing number of interventions which use a design-based approach to tackle problems associated with school effectiveness. It contributes to the identification of promising new practices and to the design of more effective instruction in the context of a national system (New Zealand) that is already generally of high quality in literacy teaching but with low equity. A specific outcome is further evidence about how new technologies and digital learning are being implemented in low SES classrooms and the relationships with valued student outcomes.