In the context of an education reform in Quebec, this case study illustrates how a science teacher's practice was redefined with nine classes over a period of four months on a specific, integrative theme inspired by issues of daily life in an attempt to increase her students' motivation and to better make sense of some scientific concepts prescribed in the new curriculum. Activity theory was used as a theoretical and methodological framework to analyze the development of the activity and revealed to be a fruitful approach to better understand real-life and complex situations within a school community. Special attention was given to dynamic relations and changes that took place as the activity was unfolding. The contribution of the nine classes in the analyzed activity was possible due to the collaboration of several members of the school community who shared the same goals and who sought to transform the learning environment. (Contains 5 tables, 8 figures, and 8 notes.)