In this study we examined whether different styles of teachers’ instructions (pro-social vs behavioural) affect the attitudes and beliefs of pre-adolescents towards peers with migrant backgrounds. The research was conducted in two countries: in Italy (N = 93) and in Russia (N = 134) among students in their last year of primary school (M age = 11.27). Teachers provided one in two sets of instructions, highlighting either the welcoming and openness characteristics of the group or its adherence to school-norms.  After receiving this recommendation, pupils read a fictional scenario depicting a fellow student from an undisclosed foreign country, with different cultural features, and who was expected to join that class-group. Children’s opinions were measured through five scales addressing the newcomer's pleasantness, positive and negative attitudes towards the respondents' (ingroup) and the newcomer's group of friends (outgroup). On an individual level, results confirm that pro-social instructions enhance positive traits towards the unknown student at a higher extent. A significant difference was also reported when comparing the two conditions on a group level: favourable characteristics were more prominent in the pro-social condition than in the behavioural one and negative traits, both in the in-group’s and out-group’s projections, were reduced. We discuss the implications of these results with regard to teachers’ impact in modelling social skills and the development of social processes in the school context.