In a highly diverse world, cultural literacy is an essential tool for living together in harmony, and dialogic teaching may be a way to promote and develop it among children and adolescents. We define cultural literacy as a set of attitudes (inclusion, tolerance, and empathy) and skills (dialogic argumentation) needed to understand others in our everyday lives. This paper focuses on the effect of a professional development programme to promote dialogue and argumentation to help children and adolescents overcome pre-existing stereotypes and prejudices and foster students’ participation in discussions that contrast divergent viewpoints. This was done through debates on social responsibility issues, living together, and belonging as presented in books and short films addressing the following topics: citizenship, the celebration of diversity, democracy, globalisation, human rights, cooperation, sustainable development, and climate change. After the professional development programme was implemented, we video-recorded two of the 15 student–teacher interaction sessions during the project’s implementation (session #3 and session #8). We analysed the data using a validated coding scheme across three educational levels (three preschool, four primary school, and four secondary school classrooms). We observed moderate gains in secondary education and preschool, but statistically significant gains in primary education.