Many researchers have been analyzing how to further improve teacher preparation -- and thus, how to improve teaching. Many of their results are based on complex models and/or on complex data analysis. Because of this complexity, future teachers often view the resulting recommendations as black boxes, without understanding the motivations for these recommendations -- and thus, without much willingness to follow these recommendations. One of the natural ways to make these recommendations clearer is to reformulate them in geometric terms, since geometric models are usually easier to understand than algebraic more abstract ones. In this paper, on the example of two pedagogical recommendations related to the other in which material is represented, we show that the motivations of these recommendations can indeed be described in geometric terms. Hopefully, this will make teachers more willing to follow these recommendations.