In this paper I argue that assessment data can be helpful to teachers for practising effective pedagogy, but it can also inhibit effective teaching when it is used to control their practice. Effective pedagogy is defined as giving each learner the resources they need to progress successfully and confidently through school. The paper first introduces the Reading to Learn professional learning program that started as a project with Indigenous students in primary and secondary schools. Both the project and the R2L program were helped and hindered by assessment regimes of education bureaucracies. Assessments developed in the program show inequalities within classrooms at all school stages, which is explained by an analysis of the literacy development curriculum through primary and secondary school. A model of pedagogy and knowledge about language is then proposed for teacher professional learning, that includes assessments that teachers control to track their students' growth. The paper concludes by advocating for professional learning that empowers teachers to take control of pedagogic practices in their own classrooms.