In the French-speaking part of Switzerland, there are official textbooks and teachers’ methodology book in mathematics, which are the same for all the elementary schools. However, these unitary resources are conceived in order to leave to the teacher a large space of freedom in the choices and in the organization of the activities. This research plans to describe how various teachers in Geneva choose, prepare and realize in class a series of activities in the domain dedicated to the notion of area. In this presentation, we will make a comparative analysis of six teachers. We will try to bring to light various criteria which occur in the choice of the activities and how the teachers prepare these activities before the class.