A new study finds that an increase in a municipality's homicide rate causes more elementary school students in that community to fail a grade than would do so if the rate remained stable.

"This finding is a source of concern because exposure to environmental violence is highly prevalent in contemporary societies and is unequally distributed along socioeconomic lines," said study co-author Florencia Torche, an associate professor of sociology at New York University. "To the extent that children living in poverty are more likely to experience environmental violence, its effect on early educational achievement will contribute to the intergenerational reproduction of poverty."

Titled, "Exposure to Local Homicides and Early Educational Achievement in Mexico," the study, which appears in the April issue of Sociology of Education, relies on data on all elementary schools in Mexico from 1990 to 2010 merged with the annual homicide rate in the municipality where each school is located.

According to study co-author Monica L. Caudillo, a doctoral student in sociology at New York University, Mexico's homicide rate grew dramatically between 2007 and 2010, from 8 to 23 murders per 100,000 people, a surge largely driven by drug trafficking-related violence.

"Our findings indicate that the recent increase in homicides resulted in thousands of elementary school children failing a grade," said Caudillo, who noted that research in the United States often focuses on the effect of violence on teenagers- and on outcomes such as dropping out of high school or getting pregnant as a teenager - but gives less consideration to younger children.

"It is an important finding that local violence adversely affects children even when they are very young - jeopardizing their long-term educational attainment," Torche said.

As for why an increase in a municipality's homicide rate increases the likelihood that children from that community fail a grade in elementary school, the authors said the effect is probably driven by heightened fear and anxiety among the kids, as well as by changes in parenting practices.

"Research shows that for children stress and anxiety result in sleep disturbance, problems with attention and concentration, and aggressive behavior," Caudillo said. "All of these factors negatively affect a child's ability to learn and succeed in school."

Regarding changes in parenting practices, the authors said past research shows that when faced with increased violence in their community, parents may resort to harsher parenting styles that may be a consequence of their own stress, as well as a strategy to protect their children from danger. Some of these reactive parenting practices may restrict children's social interactions.

"While keeping children isolated is useful for reducing their exposure to violence, it may hinder their ability to succeed in school because it may cut valuable social ties," Caudillo said.

Although the study focuses on elementary school students in Mexico, the authors said they would expect similar results in the U.S. and other countries. "The causal mechanisms explored in this study are not likely to be limited by national boundaries," Torche said. "We speculate that a similar effect results from exposure to local violence in other countries."

In terms of the study's policy implications, the authors said the findings provide another reason why nations and local communities should invest in reducing violence. "Additionally, our research suggests that in violent environments it may be important to consider initiatives such as teacher training and school programs designed to help children manage and reduce the symptoms associated with exposure to violence in order to alleviate their negative impact," Caudillo said.