In a time of abundance of resources and curriculum reform in France, we propose to analyze the evolution of teachers' practices through their interactions with resources. This contribution focus on an unexplored stage: the process of classifying a new resource selected by the teacher in one's resource system. First, the study is situated in the thread of the documentational approach to didactics and develop the concept of documentation expertise rely on Personal Information Management studies. The ability to manage and organize one's resource system is a part of the documentation expertise we want to characterize in this paper. To reach this aim, a case study of three teachers who prepared a new lesson was studied. Lastly, the concept of scheme is used to analyze data, and a component of documentation expertise is highlighted: the ability to build a classification system for resource system.