Widening gender gaps in sexual and reproductive health knowledge, attitudes, and behaviors despite equally effective sexuality education: a cluster randomized controlled trial among Chinese vocational school adolescents

Understanding gender differences in adolescent sexual and reproductive health (SRH) has implications beyond immediate health outcomes, potentially shaping future gender relations, relationship dynamics, and demographic patterns. This study examines patterns of gender divergence in SRH dimensions among adolescents and evaluates whether comprehensive sexuality education (CSE) has differential effects by gender. This is a secondary analysis utilizing the April 2019 and June 2020 survey data from a cluster randomized controlled trial implemented in 29 vocational high schools in China’s Guangdong and Yunnan provinces. Included schools should have at least 100 10th -grade students and should not have already delivered comprehensive sexuality education. Schools were randomized at the school level using a computer-generated random number generator following allocation concealment. The intervention was a web-based comprehensive sexuality education program. Analysis for this secondary study was conducted at the individual level. Multilevel linear and binary logistic regressions were used to analyze SRH knowledge, attitudes (toward power, homosexuality, premarital sex, and help-seeking), sexual behaviors, and health indicators. Three-way interactions between gender, time, and intervention were tested to examine gender differences in intervention effectiveness. The analytic sample included 2996 10th -grade students (n = 1332 control; n = 1664 intervention). Results show that while sexuality education showed uniform effectiveness across genders, natural gender divergence patterns persisted and widened. At baseline, girls demonstrated higher sexual and reproductive health knowledge and more liberal attitudes toward power and homosexuality, but more conservative views on premarital sex. Behaviorally, girls had lower odds of sexual debut and multiple partners but also lower odds of consistent condom use and higher odds of infection symptoms. Over one year, regardless of intervention status, girls showed continued gains in knowledge and increasingly liberal attitudes across multiple dimensions, while boys’ changes were limited to a modest increase in acceptance of homosexuality, though their overall attitude remained disapproving. The study reveals a pattern of persistent gender divergence in sexual and reproductive health dimensions despite uniform intervention effectiveness. These diverging patterns, which are already evident by mid-adolescence and continue to widen over one year, highlight the importance of early implementation of comprehensive sexuality education that explicitly addresses aspects on sexual and reproductive health, gender dynamics, and power relations in an analytical and critical way, while maintaining effectiveness across genders. The original randomized controlled trial, where data used in this article came from, was registered with the Chinese Clinical Trial Registry (chictr.org.cn). The registry number is ChiCTR1900021582. The trial was registered on Feb 28, 2019.