Proof is a fundamental aspect of mathematics. Without the notion of proof, mathematics would not exist as a separate subject, as it would be essentially indistinguishable from science. Yet proof is often reserved for "high ability" students in schools or those studying mathematics in further education. The author's own memories of engaging in proof at school are restricted to encountering it as an isolated topic on the A-level syllabus. Such practices deprive many students of opportunities to develop the skills and mathematical understanding they can access through activities that require them to explain, reason and justify their mathematical thinking. It also deprives them of the opportunity to understand the unique contribution the subject makes to their learning. This article describes how the author used teaching about angles as an opportunity to discuss ideas of formal proof and geometric reasoning with a Year 7 class, and discusses some lessons she has taken away from her attempt. (Contains 2 notes.)