The flaws of in-service training for mathematics teachers in Senegal have been recently exacerbated by the steady and massive recruitment of so-called Vacataires teachers with a low academic background and no pedagogical training. Besides, the dispersion of this new breed of teachers across the country and the difficulty of delocalizing their training make them less amenable to classical formulas. That is why a distant learning scheme coupled with on-site training seems a workable proposition. This study investigates the effects of a training formula based on collaborative teaching materials design. The teaching materials will be designed by trainees supervised by a teacher trainer, implemented in classes and the wash back effects observed later. This study highly values collaborative work as an instrument of materials developed from complex interactions. For a fine analysis of the pedagogical reality emerging in the classroom and assess the gap between the mathematical set ups designed in the teaching materials and their implementation by teachers, the evolution of the pedagogical reality has been envisaged as artifacts subjected to the teachers' actions and manipulations. The research concludes on a multilevel insight into the teachers' action through this instrumental approach.
