Youth-led action research has significantly influenced local and statewide policies aimed at supporting students experiencing homelessness in California. This study employs a Youth Participatory Action Research (YPAR) methodology, summarizing five years of research conducted by high school student cohorts and UC Berkeley graduate students to examine effective strategies for preventing and addressing student homelessness. The research engaged over 260 high school students, nine graduate research fellows, 31 university student mentors, and eight civic and community organizations through data collection, policy analysis, and stakeholder collaboration. Findings indicate that youth-led research strengthens alignment mechanisms, enhances cross-sector collaboration, and improves policy coordination, leading to more effective services and positive educational experiences for students experiencing homelessness. These results underscore the transformative role of youth-driven inquiry in shaping inclusive, evidence-based policies, and demonstrate the need for sustained youth engagement in policymaking to create long-term, systemic change.