The aim of this study was to generate knowledge about how teachers embark on new subject content and how their understandings of ecosystem services evolve and change in teaching practice, and also what it means to be able to discuss the relationship between the ecological and social in terms of ecosystem services in a teaching practice in middle school. The teachers used the learning study model and variation theory to explore the object of learning, by trying to design an instruction that offers fifth grade students the possibility to develop their knowledge of ecosystem services. The learning study model is an interventionist approach, where the focus is on an object of learning. A group of teachers worked together and tested students, planned lessons and implemented, evaluated and refined the lessons in an iterative process. The theoretical framework, variation theory, is a theory of learning that focuses on how discernment of aspects affects the way we perceive our world and how variation can be used to promote learning. However, since the study aims at contributing to enhancing our knowledge of how teachers can develop their skills and their meanings of a new content in practice, the empirical data from learning study was then analyzed with the help of activity theory, and the cycle of expansive learning. The result of the study shows that it can be complicated to introduce a new educational content. However, the learning study model proved to be aneffective tool for developing teachers' knowledge of ecosystem services and how to teach this. Ecosystem services were developed as teachers worked systematically with the content in their practice. For example, when the students did not respond to the exercises and to the reasoning of the ecosystem services that the teachers had planned, contradictions were created and changed the learning object's meaning for the teachers. The recordings from the lessons made the contradictions that arose during the lesson visible. Ecosystem services were developed from being primarily a tool to describe the human needs of the non-human nature to a tool to be able to discuss sustainability issues and the relationship between ecological, economic and social dimensions.