(Reuters Health) - Not only does bullying at school affect students’ emotional and social lives, it also directly affects their schoolwork and engagement in the classroom, suggests a U.S. study.

An anti-bullying billboard hangs on a building in downtown Boston, Massachusetts March 3, 2011. REUTERS/Brian Snyder

Students who faced bullying for much of their time in school had the greatest risk of low achievement and engagement, researchers found. And kids who were victimized only in earlier years showed gains in self-esteem, school performance and how much they liked school after bullying stopped.

“Bullying and peer victimization in school-age children has become more important in recent years because we recognize the damage it can do,” said lead author Gary Ladd, a psychology researcher at Arizona State University in Tempe.

“Nationally, there have been high-profile suicides and school districts trying to implement bully prevention programs,” Ladd told Reuters Health. “Teachers, parents, school administrators and anyone who knows a school-age kid should understand these effects.”

Ladd and colleagues followed 383 children - about equally split between boys and girls - from kindergarten through senior year of high school. With regular surveys, they measured the degree and frequency of peer victimization that kids experienced – including physical, verbal and relational bullying – as well as their academic self-perception and level of school engagement. They also used grades and teacher evaluations to measure academic achievement.

Based on these data, the study team categorized victimization into five types based on when it began and ended and how intensive it was. Some kids were never or rarely bullied, some were victimized in their early school years but not in later years, while another group was increasingly victimized in later years.

In Kindergarten, 21 percent of children experienced “severe” victimization and another 38 percent experienced a moderate level of bullying. These proportions declined steadily over the years until the final year of high school, when less than 1 percent were severely victimized and just under 11 percent were moderately bullied.

However, across the years, 24 percent of kids fell into the researchers’ category of “high-chronic” victimization. And these were also the ones most likely to have low school engagement, academic self-perception and academic achievement, particularly in math, the study team found.

“Some pockets of children remain bullied across their school careers,” Ladd said. “That’s a long time to be continually bullied. We’re most concerned about those kids.”

The fact that bullying typically starts in the younger grades and declines into middle school and high school runs counter to popular culture, which depicts the most severe bullying after elementary school, the authors write in the Journal of Educational Psychology.

“In the movies, you see the ‘mean girls’ in high school, but it often begins as kids enter kindergarten and learn how to assert themselves in a large group of peers,” Ladd said. “We may be waiting too late to look for warning signs.”

Among the five groups, Ladd and colleagues note that the early victims typically became less bullied over time and it would be interesting to investigate how these students were able to escape victimization as they moved through school. On the other hand, the group that was victimized later in life became more bullied by middle school and had achievement levels similar to the chronic group.

“The fact that children whose victimization levels declined over time showed improvements in academics was a very encouraging finding,” said Jonathan Nakamoto, an education researcher at nonprofit agency WestEd in Los Alamitos, California. Nakamoto, who wasn’t involved with the study, has previously researched the link between bullying and academic achievement.

“This suggests that many anti-bullying interventions could improve students’ academic outcomes as well as reduce bullying,” he told Reuters Health by email. “There are some ‘quick wins’ that teachers can do to combat bullying.”

Nakamoto pointed to the California Department of Education’s Safe and Supportive Schools program, which recommends best practices to improve school climates for learning. With bullying, the department suggests that teachers and parents educate themselves about different types of bullying, create “safe spaces” to talk, and take action when students seem isolated.

“When children are just starting school, pay attention to certain comments about kids not liking them or not letting them play,” Ladd said. “Take it seriously. Our ‘boys will be boys’ and ‘girls will be girls’ mindset prevents us from seeing what’s happening.”

SOURCE: bit.ly/2kRRBS2 Journal of Educational Psychology, online January 30, 2017.