In what ways can an approach, where teachers systematically investigate what it takes to learn and how the content taught is perceived by the learners, be a possible way to enhance student learning? This is discussed from an example where a group of teachers collaboratively used a systematic approach to investigate what it takes to learn to subtract negative numbers in grade seven and eight in a Swedish compulsory school. In this approach, student learning and their understanding of that which was taught was the main concern and in the fore of the teachers’ attention. In an iterative process of planning, observing and revising a single lesson, they in depth analysed and inquired the progress of student learning before, in and after the lesson. In this process the teachers tried to gain knowledge about the particular obstacles their students had for learning what was intended. This was done from an analysis of students’ written tests and from a close observation of video recorded lessons. In this observation, they tried to understand what possibilities and obstacles there was for learning. Through the process they gained some insights from which they successively could change their teaching in a way that appears to have promoted students’ learning. Our aim is to demonstrate how reflection on teaching and the learning from teaching can take its point of departure from sensitivity to students’ understanding and perceptions of that which is to be learnt.