The purpose of this research is to learn how youth aged 11–14 understand highly aggregated data about social and economic conditions, especially related to the United Nations Sustainable Development Goals. We designed an after-school program that introduces students to data broadly in the context of “using data for social good.” Using CODAP, an educational data visualization tool, students explore data about countries’ health and education indicators. We observe that youth are highly engaged with these data yet sometimes struggle to make sense of the aggregate values that hide variability within countries. Using examples from student projects, this paper reports preliminary findings about how youth analyze data aggregated by governmental entities such as countries, states, or cities.