Today, data is no longer just important to computer science. Instead, basic competencies in managing, processing and using data are necessary in almost all other sciences and even in everyday life. Such competencies empower students to handle their own and others’ data adequately and allow them to use data-related technologies and tools in a critically-reflected way. Although aspects of this topic are typically already part of computer science curricula for secondary schools, particularly fostering data-related competencies is often not the focus, so that large parts of this exciting topic have not arrived in the classroom yet. In this paper, we investigate the exemplary topic data analysis and predictions from a secondary education perspective. After summarizing the technical and didactic foundations, we describe a theoretically sound teaching concept which aims to foster the acquisition of basic competencies in this field and to contribute to a better understanding of these important aspects of the digital world. Besides presenting the teaching concept, the paper discusses the methodical structure as well as the software tool used. In addition, the mostly positive results and impressions of an evaluation with ninth-grade students are presented.