Comprehensive sex education (CSE) is a foundational element for promoting gender equity, sexual autonomy, and reproductive health among adolescents. However, sociocultural taboos and limited institutional support often hinder its effective delivery, particularly in contexts marked by gendered power imbalances. This study aimed to explore female adolescents’ perceptions of sex education in a vocational high school setting, assess the extent of their knowledge, and examine how these perceptions are shaped by broader gender norms and institutional factors. A cross-sectional descriptive study was conducted among 30 tenth-grade female students at Taruna Tekno Nusantara Vocational High School in Deli Serdang, North Sumatra, Indonesia. Data were collected using a validated structured questionnaire focusing on knowledge levels, attitudes toward sex education, and opinions on its delivery through schools. Descriptive analysis was conducted using JASP version 19. Findings reveal that 66.7% of students were only somewhat knowledgeable about sex education, and an identical proportion deemed it unimportant. However, 73.3% recognized its critical role in enhancing reproductive health literacy and shaping respectful gender interactions. While 53.3% supported school-based sex education, 46.7% remained opposed, reflecting persistent sociocultural resistance. The study highlights a disjunction between adolescents’ knowledge and the recognized importance of sex education, underscoring how internalized gender norms and inadequate institutional engagement perpetuate informational and empowerment gaps. Embedding CSE within rights-based, participatory, and gender-transformative frameworks is vital for promoting health equity and fostering adolescent agency.