In academic literature that supports school-based sex education, adolescence is presented as the main stage of sexual development (Lesko, 2001). It is the time in which healthy habits in regards to sexuality are formed, and therefore, from a health education perspective, the time to deliver sexual health interventions (Schaalma et al., 2004). In this life stage, beginning to engage in sexual activity is considered to be normal in the Netherlands (Schalet, 2011), adolescents are seen to be at risk of several negative influences. These risks are mainly silence about sexuality by parents (Smerecnik et al., 2010), peer pressure (Bay-Cheng, 2017), the internet and media more generally, and hormones (that cause changes in body and brain).
The theoretical underpinnings of this type of sex education, that derive from social psychology (Ferguson et al., 2008; Miedema et al., 2011; Schaalma et al., 2004), also guide effectiveness studies on knowledge, attitudes and intentions for behaviour (Schutte et al., 2014; Vanwesenbeeck et al., 2015)