This study explores the relationship between collaborative dynamics, expressed through observed leadership behaviour, and skills. It is based on the mechanical design activity of six dyads of students (post-secondary vocational training), composed of 11 boys and one girl, who are improving an existing mechanical system. Actions are studied using principal components analysis (PCA) and hierarchical clustering to identify collaborative dynamics in teamwork and their links with scores in standardised spatial tests. Results reveal two profiles of collaboration characterised by two leadership styles, typically identified as autocratic leadership and participative leadership. We highlighted a relationship between leadership posture and spatial skills level, although leadership style does not seem to depend on the spatial skills of the teammates. In addition, we have implemented a methodology based on the actions initiated, to identify leadership posture and leadership styles. This methodology could be complementary to the one currently used and based on questionnaires.