This paper aims to characterize the nature of powerful knowledge engaged in by students at school, especially in physical education. This study is based on a basketball (BB) lesson that was observed in a summer camp for children aged 10 to 15 in Senegal (YaThi'Breizh Association, Thiès, 2017). The lesson’s goal was to improve the quality of the dribble. The question is what is it essential to be learnt so that the players can make dribbling effective in an authentic game context. This question is approached through the notion of epistemic kinship (Loquet, 2016; Loquet, 2017). The term "epistemic" is seen as synonymous with "concerning the knowledge involved in a situation". In turn the notion of epistemic kinship is linked to that of "family resemblance" (air de famille) proposed by Wittgenstein (Chauviré and Sackur, 2003). This is defined in articulation with savant knowledge. "Savant" is used in a generic sense to qualify the oeuvre of those who invent and produce knowledge. Thus, a savant is one who, in the social and cultural world, knows (does) something (an oeuvre) as "practical connoisseur" of this oeuvre. For example, Fosbury is savant (connoisseur or expert) of the ‘Fosbury flop’. Basketball practices, at school or in sports clubs, have their own logic: finalities, rules and values that the institution generates. We can note differences that mark the identity, or the specificity, of each of these practices. With regard to the term "difference" or “differentiation”, we propose the notion of "gap" (Jullien, 2012) which is related to a distance without implying an identity established a priori. Accordingly, school and sports practices are seen as kinship-based, and both activities are considered as creative processes of transformation. In order to understand the nature of powerful knowledge it is necessary to address the gap between school and sports practices i.e. how far or how close is the gap between school and sport knowledge? In this case study, attention is focused on two dribbling strategies: those of students satisfying the teacher and those of high level BB players' activity chosen as cultural reference at school. It is then necessary to understand: on the one hand, the kinship problem that faces players whether they are novice or expert, and on the other hand, the kinship way in which they solve this problem.

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