What are the specific and essential things that ought to be taught? On which precise base is a given progression proposed and, more specifically, are articulated the levels determined by teachers? This questioning fundamentally goes beyond the classical thoughts about the relationship between social practice and school practice. An authentic ethology of student behaviour in team sports must be established in connection with reference settings and based on valid assessment tools. Nevertheless, the interpretation of observed behaviours will lay more on the nature of the tactics used than on the correction of technical errors. In this paper, we will first consider, through French and German literature, historical aspects of the development of what we shall call the "Tactical-Decision Learning Model". Then, we will submit an attempt at modeling players' activity in invasion team games. Selected descriptions of students' conduct deal only with successful set-ups, that is, those which, without loss of the ball, lead to a shot on goal. (Contains 11 figures.)