This cross-lagged longitudinal study examines the evocative impact of a child's psychological adjustment on teachers' affective response and instructional support for a child, and the influence this support and response has on the child's subsequent adjustment. A hundred and seventeen Finnish teachers self-rated the instructional support they gave, and the affect they experienced while teaching 307 children from school grades 1, 2 and 3. Teachers also rated the level of prosocial and externalizing problem behaviour among children. Results showed that the more children exhibited externalizing problem behaviour in grades 1 and 2, teachers not only did provide more instructional support for them a year later but, at the same time, they reported feeling less positive affect. Low levels of positive affect were also reported by teachers a year later with regard to children who had received more instructional support from them in grades 1 and 2.