The benefits of health promotion are now well documented. However, the interventions implemented among a target population or in specific settings, such as schools, must be effective. Many initiatives today rely on the goodwill of grassroots actors—whether from community organizations or institutions—who are feeling their way forward, improvising, and experimenting. But since the programs implemented are not always evaluated, it is difficult to know their actual impact, even if the beneficiaries report being satisfied. Based on this observation, this issue of La Santé en action advocates for the implementation of interventions recognized as effective in order to improve the prevention system. Impact assessment and cost-effectiveness analysis are crucial, even if they are perceived as complex and time-consuming. It is equally important to provide practitioners—who design programs—with validated resources that can be used in their professional context, encouraging them not to start from scratch. Access to this scientific knowledge—whether national or international—is now being organized in France across various fields, signaling the beginning of a shift toward evidence-based prevention.