This study aims to analyze how the synergy between teachers and parents in instilling digital media discipline helps prevent smartphone addiction among elementary school students in Semarang. The study employs a qualitative approach using a case study design, in which data were collected through in-depth interviews with teachers and parents, as well as observations of classroom learning activities. The results indicate that smartphone dependency significantly impacts students' academic, social, and emotional development, characterized by reduced focus on learning, weak self-control, and diminished social interaction and empathy. To address this, three primary forms of synergy between teachers and parents emerged: intensive communication, the establishment of shared rules, and alternative educational activities. Continuous communication fosters shared perceptions and strategies for managing children's device usage. Meanwhile, consistent rules at school and home, as well as engagement in positive activities, have proven effective in fostering students' digital discipline. Theoretically, the findings of this study align with Albert Bandura's Social Cognitive Theory, particularly the concepts of self-regulation and reciprocal determinism, which explain that children's behavior is influenced by the interaction between individual, environmental, and behavioral factors. This suggests that a shift from passive supervision toward active collaboration is necessary to make smartphones a purposeful and valuable learning tool. The contribution of this study lies in the development of a practical collaboration model between teachers and parents based on digital literacy to prevent smartphone dependency among students starting from elementary school age.