Rough and tumble play has been found to be positive for physical, social and cognitive development; it is often erroneously misinterpreted as aggression and generally stopped by preschool teachers. The current study sought to examine the relationship between teacher training and education and judgements about aggression in children. Ninety-four preschool teachers currently working in child care centres viewed two videotapes depicting preschool-aged boys engaged in naturally occurring outdoor play. Participants scored the tapes for occurrence of aggression, using their own definition. Results indicated that child care providers with a four-year college degree in early childhood education reported less aggressive behaviours than those without a college degree. Novice child care providers reported higher levels of aggression than more experienced preschool teachers; child care providers with similar education/experience were more likely to report aggression within the same observation segment. These findings suggest that education may support more accurate assessments of aggressive play.