The present study investigated the expression of emotions in pupils of the first five grades of primary school. The sample ( N = 114) comprised pupils aged between 6.5 and 10.6 years, whose expression of emotions was observed using an observational schema. Observations were gathered in classrooms at 70 schools in different regions of Slovenia. Fourteen emotions were recognized in the pupils’ expressions, with joy and anger predominating. The intensity of the expression of positive and negative emotions, as well as basic and complex emotions, was moderate, and no significant difference in intensity was observed between these categories. Boys expressed more positive, negative and basic emotions than girls. The situations that elicited emotions varied and reflected the prominent issues in school, particularly academic achievement, social interactions with teachers and classmates, and activities during lessons. The applicability of the results to teachers’ work in the classroom was highlighted.