This paper critically examines the design and impact of two commonly used education platforms for reading, "PM eCollection" and "Epic." Framed by a data justice lens, the study employs a walkthrough methodology to examine the ways each platform (re)configures teaching and learning practice, and more broadly schooling. The study extends the method by engaging three primary school teachers in the walkthrough process embedded in their practice. Findings demonstrate significant asymmetries in the value derived from the data practices of the digital reading platforms by teachers, schools and EduTech companies. While of limited value in teacher's practice, the use of the digital platforms and data has implications for the way reading is represented, students are made visible and treatment of teachers, students and families.