School bullying has been investigated by looking at either the frequency of bullying or the perceived severity of being bullied. However, the relationship between these two constructs needs further clarification. The aim of this study was to clarify the connections between the frequency and the perceived severity of being bullied for bullying intervention and prevention, and examine gender differences in these two constructs. The participants consisted of 1423 secondary school students in southern Taiwan. The 21-item School Bullying Scales with Frequency and Severity were administered. Using Rasch analysis, the two subscales of frequency and severity were aligned on the interval logit scale to yield four quadrants. Results showed that the two latent traits derived from the two subscales had a weak correlation (r = -0.11). Some bullying behaviours, including "one's friendship being ruined", "belongings taken without permission", "being hit and kicked", "being spoken ill of in public", and "being ostracised", were perceived as the most severe and most frequent behaviours. Boys reported to be more frequently bullied than girls were, whereas girls perceived bullying to be more severe than boys did. It was suggested that bullying behaviours perceived as higher severity and frequency deserve greater attention.