Comprehensive Sexuality Education (CSE) is a lifelong learning process that begins in early childhood. International literature and guidelines emphasize the necessity of CSE in the school environment, highlighting educational and teaching staff training needs. However, Italy lacks a law supporting CSE in schools and has no initial training curriculum for teachers and educators focused on CSE topics. In undergraduate programs for early childhood and primary school education, topics related to sexuality are rarely addressed. Training is offered in the Italian context, typically through specific courses that individuals can voluntarily undertake; however, a significant challenge is that these courses often come with high costs, making them inaccessible to many. Within this sociocultural, educational, and training context in Italy, the educational project for the EDUSex Open Badge was developed at the Sapienza University of Rome as part of the Open Badge EDU Sapienza and service-learning framework. This elective and no-cost course is specifically designed for educational and training degree program students. The course consists of 12 in-person sessions, with one three-hour meeting per week, following a pilot training program offered during the 2023-24 academic year, including in-person and online sessions for two three-hour weekly meetings. The course has been adjusted based on student feedback, including only weekly three-hour in-person sessions. The project aims to promote methodologies and skills to address educational, social, and practical needs through participatory activities. Additionally, the course helps students reflect on their concepts, sexual scripts, beliefs, and attitudes toward sexuality and CSE, enabling them to separate their personal perspectives from scientific and accurate information in the future. The course covers a wide range of CSE topics, including sexual health, sexual identity, rights, the LGBTQIA+ community, emotions and relationships, consent, respect and gender-based violence, contraception, sexually transmitted infections, sexual development, sexual pleasure, stereotypes, socio-cultural and personal influences, and educational planning for CSE across different age groups. Competency evaluation includes three formative assessments: the first involves small group work in which students present an insight into a chosen topic; the second requires each student to design an educational or teaching project to propose to schools hypothetically; and the third is a written test to assess knowledge gained from the training. This three-step assessment is accompanied by initial and final questionnaires that evaluate knowledge and attitudes.