Sexual harassment, defined as making an unwelcome behavior of a sexual nature, is highly prevalent all over the world. In this study sexual harassment in high schools is studied as this is one of the places where it has the highest prevalence and a time in life where an intervention can have the highest impact. Even though there are studies about sexual harassment preventive programs in schools, few of them consider the cultural differences, beliefs, and expectations of specific communities. This study fills that gap by focusing on the social norms around the behavior. Mixed methods were used, combining quantitative and qualitative techniques. Focus groups were done and a questionnaire was applied to identify the most common sexual harassment behaviors, as well as the existence or absence of personal normative beliefs, empirical expectations, and normative expectations around the phenomenon. Results evidenced that there are different normative and empirical expectations for girls and for boys that also vary depending on the specific type of harassment. Subtle types of sexual harassment for boys can be classified as a social norms; in other words, their motivations are not independent but socially conditioned. Furthermore, students expressed different factual beliefs about victims and perpetrators depending on their gender. The findings provide diverse evidence about how individual and interpersonal beliefs and expectations are related to sexual harassment in schools. Understanding these social processes is useful for designing culturally and socially grounded interventions for sexual harassment prevention in high schools.