We describe in this article the results of three-years study of using a Tangible Tabletop Interface (TTI) for the development of student learning in spatial reasoning abilities. In partnership with the French Department of Education and teachers, we have designed and built a serious game in mathematics, called The Game of Towers for the TangiSense 2 interactive tabletop. Then, we conducted « in the wild » experiments with 68 students. As part of a first study, we compared the learning outcomes of two groups of students (Gr. Traditional vs. Gr. TTI). The results of this study have encouraged us to make a second experiment. In the latter, we analyzed child participation (physical and verbal) and the social modes of knowledge co-construction when they played the game on the TTI. The results showed that students improved their performance by playing the game on the TTI and collaborated through externalization and conflict-oriented consensus.