For the first time, the 2015 round of PISA collected data on students’ exposure to bullying. These data show that bullying is widespread. On average across OECD countries, around 11% of students reported that they are frequently (at least a few times per month) made fun of, 8% reported that they are frequently the object of nasty rumours in school, and 7% reported that they are frequently left out of things. Being bullied can negatively affect academic achievement because it influences students’ capacity to focus on academic tasks. Schools where the incidence of bullying is high by international standards (more than 10% of students are frequently bullied) score 47 points lower in science, on average, than schools where bullying is less frequent (schools where less than 5% of students are frequently bullied). These relationships suggest that bullying can both stem from and may exacerbate students’ disengagement with school and underperformance.