Most of the research that informs our understanding of children’s social-emotional learning (SEL) comes from Western, Educated, Industrialized, Rich, Democratic (WEIRD) societies where behavior is guided by a view of the self as autonomous, acting on individual preferences. In the subsistence agricultural communities (home to more than a quarter of the world’s population), obligations and communal goals override personal preferences and individuals see themselves as part of a social hierarchy. These contrasting models of the self have profound implications for SEL. Many studies underestimate these implications because they use assessment tools developed in WEIRD settings to understand SEL in lower- and middle-income countries. The aim of our study was to build an SEL assessment from the ground up, based on community definitions of valued competencies in southern Tanzania. In Study 1, Qualitative data from parents and teachers indicated that dimensions of social responsibility, such as obedience and respect, were valued highly. Teachers valued curiosity and self-direction more than parents, as competencies required for success in school. Quantitative assessments in Study 2 found that individuals more exposed to sociodemographic variables associated with WEIRD settings (urban residence and higher parental education and SES) were more curious, less obedient and had poorer emotional regulation. Overall findings suggest that the conceptualization of social-emotional competencies may differ between and within societies; commonly held assumptions of universality are not supported. Based on the findings of this study we propose a systematic approach to cultural adaptation of assessments. The approach does not rely solely on local participants to vet and adapt items but is instead guided by a rigorous cultural analysis. Such an analysis, we argue, requires us to put aside assumptions about behavioral development and to consider culture as a system with an origin and function. Such an approach has the potential to identify domains of SEL that are absent from commonly used frameworks and to uncover other domains that are conceptualised differently across contexts. In so doing, we can create SEL assessments and SEL programs that are genuinely relevant to the needs of participants.