In this study we investigated the relations between reactive and proactive aggressiveness in pupils and a perceptual orientation described as interest in signs of weakness in a teacher who is new to the class. Self-reported data were collected from a sample of 10th grade pupils. There was a substantial and significant relation between proactive aggressiveness and a perceptual orientation towards weakness in teachers new to the class. Reactive aggressiveness was significantly but weakly related to perceptual orientation towards weakness. Results are discussed as adding to knowledge about the two types of aggressiveness, and as information that can guide teachers' practice. (Contains 3 tables.)