Increasing participation in school meals could reduce food insecurity and improve dietary quality, especially for low-income children, but low-cost, scalable strategies for increasing participation in school meals have not yet been identified or evaluated. This study will design and rigorously evaluate a marketing campaign to encourage participation in school meals. The study has three aims: (1) Develop a marketing campaign encouraging school meal participation; (2) Evaluate the impact of the marketing campaign on school meal participation in a RCT; and (3) Convene key stakeholders to review findings and develop next steps and policy recommendations. The study will use a combination of qualitative semi-structured interviews, an online RCT with parents of children in grades 1-5, and an online convening to identify policy recommendations.