Comprehensive sex education (SE) is crucial in promoting sexual health and responsible behavior among students, particularly in elementary schools. Despite its significance, teaching SE can be challenging due to students' attitudes, shyness, and emotional barriers. Socially assistive robots (SARs) sometimes are perceived as more trustworthy than humans, based on research showing that they are not anticipated as judgmental. Inspired by those evidences, this study aims to assess the success of a SAR as a facilitator for SE lessons for elementary school students. This study conducted two experiments to assess the effectiveness of a SAR in facilitating SE education for elementary school students. We conducted two experiments, a) a group activity in the school classroom where the Nao robot gave a SE lecture, and we evaluated how much information the students acquired from the lecture, and b) an individual activity where the students interacted 1:1 with the robot, and we evaluated their attitudes towards the subject of SE, and if they felt comfortable to ask SE related questions to the robot. Data collected from pre- and post-questionnaires, as well as video annotations, revealed that the SAR significantly improved students' attitudes toward SE. Furthermore, students were more open to asking SE-related questions to the robot than their human teacher. The study emphasized specific SAR characteristics, such as embodiment and non-judgmental behavior, as key factors contributing to their effectiveness in supporting SE education, paving the way for innovative and effective approaches to sexual education in schools.