This study is aimed at understanding the importance of the opportunities to learn (OTL) offered by a teacher in his classroom in facilitating the acquisition of mathematical competence (CM) of their students. In this paper we present the empirical part of this research, which consisted in the study of two cases (in Spain and Armenia) and documents the results in light of the theoretical model OTL-CM, which emerged in the analytical process. The results show that the scarcity OTL that promote meaningful learning of mathematics limits the acquisition of mathematical knowledge and basic skills, as well as the capacity to apply them to daily life situations.