Children who have a good relationship with their teacher may be protected from expressing aggression¹ and being the target of aggression at school. That's the key finding in a new study of Canadian first graders that appears in the journal Child Development. The study was conducted by researchers from the University of Quebec at Montreal, Laval University, the University of Alabama, the University of Montreal, and University College Dublin.

"Aggressive behavior in middle childhood is at least partly explained by genetic² factors, but genetic influences on behavior usually don't operate independently of environmental influences," notes Mara Brendgen, professor of psychology³ at the University of Quebec at Montreal, who led the study.

Researchers studied 217 Canadian identical and fraternal twin pairs at age 7 to delve⁴（钻研） into the interplay between nature and nurture⁵ involving the source of aggression in the children. Twin pairs weren't in the same classrooms, but had different teachers and different classmates. Classmates rated the twins' level of aggressive behavior and the extent to which they were victimized by peers. The twins' teachers rated the quality of their relationship with each twin. Genetic effects on aggression were estimated by comparing the similarity in behaviors of identical and fraternal（兄弟般的） twin pairs.

The study found that children who were genetically⁶ vulnerable to being aggressive were more likely to be victimized by their classmates than others. However, these children were protected from acting⁷ aggressively and being the target of other children's aggression if they had a very good relationship with their teacher -- a relationship that was warm and affectionate（深情的） and involved open communication.

"Children's relationships with teachers and with peers in school play a critical role in shaping their social-behavioral development," notes Brendgen. "Our study found that a good relationship with the teacher can protect genetically vulnerable children from being aggressive and, in consequence, from becoming the target of other children's aggressive behavior."

The findings can inform interventions⁸ aimed at addressing children's aggression, and can also be used in teacher-training efforts.

The study was supported by the Social Sciences and Humanities Research Council of Canada, the Fonds Concerté pour l'Aide à la Recherche⁹, the Fonds Québécois de la Recherche sur la Société et la Culture, the Canadian Institutes of Health Research, and the Fonds de Recherche en Santé du Québec.