This Research to Innovative Practice Full Paper presents a multidisciplinary, design-based research study that aims to develop and study pedagogical models and tools for integrating machine-learning (ML) topics into education. Although children grow up with ML systems, few theoretical or empirical studies have focused on investigating ML and data-driven design in K-12 education to date. This paper presents the theoretical grounds for a design-oriented pedagogy and the results from exploring and implementing those theoretical ideas in practice through a case study conducted in Finland. We describe the overall process in which middle-schoolers (N = 34) co-designed and made ML applications for solving meaningful, everyday problems. The qualitative content analysis of the pre-and post-tests, student interviews, and the students' own ML design ideas indicated that co-designing real-life applications lowered the barriers for participating in some of the core practices of computer science. It also supported children in exploring abstract ML concepts and workflows in a highly personalized and embodied way. The article concludes with a discussion on pedagogical insights for supporting middle-schoolers in becoming innovators and software designers in the age of ML.