WEDNESDAY, Oct. 26 (HealthDay News) -- Having a good relationship with their teacher may help reduce aggressive behavior among first-graders and also protect them from other students' aggression, researchers have found.

Genetic factors can influence aggression in middle childhood, but outside influences also play a role, according to the study published in the September/October issue of the journal Child Development.

For the study, Mara Brendgen, a psychology professor at the University of Quebec at Montreal, and colleagues looked at 217 identical and fraternal 7-year-old twin pairs in Canada. The children in each twin pair had different teachers and classmates.

The twins' levels of aggressive behavior and the amount of aggression they experienced from others were rated by their classmates. The teachers also rated the quality of their relationship with each twin.

In addition, the genetic effects on aggression were estimated by comparing the similarity of behaviors in the twin pairs.

The researchers found that twins who were genetically vulnerable to being aggressive were more likely to be picked on by classmates. But these children were less likely to act aggressively or to be the target of classmates' aggression if they had a close relationship (warmth, affection and open communication) with their teacher.

The findings might prove helpful in developing programs to deal with children's aggression and in teacher training, according to the study authors.

"Children's relationships with teachers and with peers in school play a critical role in shaping their social-behavioral development," Brendgen said in a news release from the Society for Research in Child Development.

"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," Brendgen added.

More information

The American Academy of Pediatrics has more about aggressive behavior.