One difficulty with the Swiss dual system is the gap between the practical work in the company and the theoretical teaching at school. In this article, we examine the case of carpenters. We observe that the school-workplace gap exists and materializes through the importance given to drawing classes at school, while carpenters almost never draw at their workplace. The existence of the drawing classes are justified by their contribution to the development of spatial skills, which are essential to carpenters. To gain a clearer view on spatial skills for carpenters, we performed a large-scale (n=512) field study on spatial skills, in which carpenters were compared with logistics apprentices and high school students. We report the results of this study and show that carpenters’ spatial skills are higher than the two other populations’ but that they do not improve between the end of the first year and the end of their apprenticeship. Those results give us indications on how to build a future learning environment to improve the training of carpenters.