After a friend was shot dead, Richard Bryant, 16, noticed he couldn't do simple things, like schoolwork.

"I just lost the will to read," said Bryant, a junior at Central High School. His buddy, Khaleef Zayre Johnson, 22, was shot twice in the back and killed outside the Spring Garden Apartments in January. No one has been arrested in the shooting.

"My concentration skills went down a lot," Bryant said. "I had a book to read and didn't read it at all."

Without realizing it, Bryant was corroborating aspects of recent research by a sociologist from New York University.

Children living in areas where homicides are committed have lower reading and verbal test scores, according to the study by sociologist Patrick Sharkey. His work is based on research he did in Chicago.

Sharkey said children don't even have to know the victims, as Bryant did.

It's as though children in poor, crime-ridden neighborhoods live perpetually behind yellow police crime-scene tape, never too far from the shooter, the victim, and the bullets that streak between them.

"The study shows what it's like for a child to carry the burden of someone dying when that child is told to sit and read," Sharkey said in an interview.

According to Sharkey's research, the closer the homicide is to a child's home, the more dramatically the child will be affected. Conversely, effects were weaker when the homicide was many more blocks away.

"After a killing, kids' ability to maintain attention is compromised," Sharkey said. "The stress affects learning."

To measure the effects, Sharkey compared the test scores of children who were assessed directly after a homicide in their neighborhood with the scores of children from the same area - not necessarily the same children - taken before the killing.

They scored dramatically lower than others in the same neighborhood before the homicide, Sharkey said.

"It's tangible, concrete evidence that the specifics of the incident affect the kids," he said.

Sharkey found that the effect of a local homicide is to reduce children's performance to a degree that's equivalent to missing between two to four years of schooling, especially among African Americans.

The effect of a local homicide wears off after 10 days, but the consequences of each incident accumulate over time, leading to long-term impacts on children's academic trajectories, Sharkey said.

What's fascinating - and, so far, impossible to explain - is while the reading scores of African Americans were greatly affected, the scores of Hispanics were hardly different, Sharkey said. Whites were not studied, Sharkey said, because there were no neighborhoods in which white people were exposed to the same levels of violence.

Sharkey said he will continue researching to understand why the African American response was so powerful.

Such research needs to be considered as people discuss the performance of students in the Philadelphia schools, said Maria Kefalas, a sociologist and expert on violence at St. Joseph's University.

"When school officials want to raise test scores, it has to be hand in hand with dealing with violence," Kefalas said. "Children can't learn if they're exposed to high levels of violence. It has to be seen as a learning issue."

The stress hormones released within children in proximity to violence are akin to what soldiers experience in combat, she said.

"Stress chemicals clog your brain and you can't concentrate," Kefalas said.

Living near a murder scene is one among many major risk factors suffered by inner-city children, noted Philippe Bourgois, a University of Pennsylvania anthropologist who studies crime and public health.

Bourgois said proximity to murder is linked with "poverty, lack of access to good, safe schools, lack of access to supportive public infrastructure and services, exclusion from social networks, and hyper-segregation."

Richard Bryant knows that in safer neighborhoods, "regular 16-year-olds don't have friends dying from being shot."

"But where I live," he said, "it's always in the back of your mind. It just hurts you mentally."