Adolescents and young adults (ages 15-39) represent the only U.S. age group with rising cancer incidence, underscoring the need for early prevention. Yet, awareness of cancer risk factors among adolescents remains low, and few evidence-based programs are integrated into school curricula. The Cancer Risk Education in Schools for Youth and Families (CARES4You) study aims to co-design a middle school cancer prevention curriculum with teachers to ensure feasibility, alignment with science standards, and relevance to students' lived experiences. Using a mixed-methods approach, data were collected through three complementary sources: (1) Focus groups with 39 teachers and administrators from five New York City public middle schools explored curriculum content, classroom fit, and caregiver engagement. Sessions were recorded, transcribed, and analyzed thematically; (2) Classroom observations (n = 6) documented instructional context, student engagement, teaching strategies, and resource availability, with field notes analyzed descriptively; and (3) Content field testing with Math for America (MƒA) fellows (n = 33) piloted two curriculum units on nicotine and dietary-related cancer risk. Teachers completed structured surveys and provided open-ended feedback on feasibility, clarity, and engagement. Data across all sources were triangulated to identify convergent themes related to feasibility, implementation, and contextual adaptation. Teachers viewed the curriculum as relevant, flexible, and culturally resonant. Six themes emerged: teacher receptivity, environmental context, lessons beyond the curriculum, integration strategies, effective practices, and caregiver engagement. Respondents valued hands-on learning and real-world connections but cited limited time and resources. Integrating teacher co-design with cancer prevention represents a promising, sustainable strategy to enhance adolescent cancer literacy and intergenerational health awareness.