Persistent inequities in access to quality STEM education continue to limit educational and socio-economic opportunities for underserved youth in Nigeria, particularly in low-resource urban, peri-urban, and rural communities. This study examines the effectiveness of a participatory, tech-enabled STEM education model grounded in community-based volunteering initiatives. Using a qualitative-dominant mixed-methods design informed by participatory action research, the study investigates how co-designed EdTech interventions influence learning outcomes, youth engagement, agency, and community ownership. Empirical findings demonstrate significant improvements in STEM knowledge, practical problem-solving skills, digital literacy, and learner confidence, alongside measurable increases in participation, peer collaboration, and self-efficacy. Beyond academic gains, the results reveal broader empowerment effects, including enhanced learner agency and shifting community perceptions regarding the relevance and value of STEM education. The study further identifies structural constraints related to infrastructure, connectivity, volunteer capacity, and scalability, highlighting the limitations of donor-dependent and pilot-driven education models. By foregrounding practitioner-led and volunteering-based insights, this research advances participatory education and EdTech scholarship from a Global South perspective, emphasizing the role of contextual adaptation and community ownership in sustaining educational interventions. The findings inform policy and practice by proposing design principles for scalable, inclusive, and sustainable STEM education initiatives tailored to low-resource environments.