Current literature argues that the lack of skills for users to engage in Open Data ecosystems is a primary barrier to expanding the benefits of Open Data in society. Although schools have been identified as potential actors in promoting Open Data literacy goals, educational approaches to support this aim have not been clearly defined. Our previous research on Open Data skills definition indicates that focusing on data literacy and real-world problem-solving is crucial in Open Data Education. In the current study, we apply a design-based research methodological framework to investigate how learning designs for building Open Data competencies in elementary school can be developed and what educational design elements are relevant. Design-based research proposes iterative cycles including problem definition, design, intervention, analysis and redesign. An exploratory cycle from problem definition to the first intervention with an educational open data design has been conducted. Central design elements, including elements of game-based learning, are identified by reviewing the domains of data literacy and real-world problem-solving. An educational design was tested in a Danish school with 39 pupils aged 15 to 16 in 9th-grade and five teachers. Following a thematic network analysis methodology, the results provide a contextual understanding of the competencies and skills for using Open Data in elementary school, how to keep students interested and engaged, and the importance of authenticity for Open Data learning designs. We propose a game design, making a parallel between learning and game design elements. The game design uses Open Government Data, and authentic Open Data practices for engaging elementary school students in developing Open Data competencies. Our study contributes to the understanding of social contexts and new technologies in the Open Data field showing the value of real-world applications and public value generation using Open Government Data.