As a multifaceted concept, the learning of angle concepts takes years to achieve and is beset with challenges. This paper explores how the processes of constructing and validating a learning progression in geometric reasoning can be used to generate targeted teaching advice to support the learning of angle concept. Data from 1090 Year 4 to Year 10 students' ability to reason about geometric properties and deduce angle magnitudes were analysed. Rasch analysis resulted in eight thinking zones being charted. Students' responses to the angle items within this larger data set were analysed with a focus on how reasoning about angles developed. The result is a five-stage framework for learning angle concepts.