The objectives of this article are, first, to assess the self-awareness that future primary school teachers have on their role in integrating international students into school and society; second, to determine the importance they give to multiculturalism and multilingualism to develop the communicative competence of their international students. This work is an extension of previous research, started in 2019, with the overall objective of analyzing the sustainability of education systems regarding their current cultural and linguistic diversity. The research question is whether future primary teachers know both assessed aspects. The main problem lies in the initial training in the national language. Its initial design contemplated a context where all students were native speakers. However, the percentage of students with different cultural and linguistic backgrounds has continued to increase. Therefore, communicative competence is crucial for their academic and social inclusion. Through quantitative methodology, the future primary education teachers participated in a survey that addressed these issues. The results demonstrated that training in this aspect makes them aware of their role as mediators and social agents for inclusion. According to the findings, revising initial teacher training in didactics of the language is crucial.