Holistic concepts like culture have faced criticism for potentially shielding research from rigorous empirical testing. This study investigates whether cultural distinctions between Swedish-speaking and Finnish-speaking students can be empirically supported: that is, the microfoundations of school cultures. Specifically, the study compares the antecedent of sisu (self-discipline) among 15- to 17-year-old Swedes, Finnish-speaking Finns, and Swedish-speaking Finns. Using structural equation modelling on crosssectional survey data, we estimated and compared path coefficients and descriptive statistics from 2,691 participants. The findings reveal notable differences among Finnish-speaking Finns concerning the relationship between internet use in school and sisu, which also manifest as genderspecific differences, as the negative association between increased internet use in class and sisu is more pronounced among boys than girls. This gender discrepancy is less evident among Swedes and Swedish-speaking Finns. Another significant finding pertains to the relationship between obedience and sisu among Finnish-speaking Finns. For girls, there is a moderate positive association, while no such relationship exists for boys, indicating that Finnish-speaking girls are more likely than boys to respect teachers’ authority. This gender difference is not observed among Swedish-speaking Finns or Swedes. Overall, Swedish-speaking Finns exhibit path coefficient patterns more similar to Swedes than to Finnish-speaking Finns.