The classroom falls silent as the teacher explains that victims of violence go through specific psychological stages in the aftermath of an attack. Most of these students, though, don't need a lecture to understand the lesson. It's part of their everyday lives.
Many of the teens came to the U.S. seeking refuge from Mexico's drug war, which made violence a constant companion since childhood.
"I've been through all three stages: impact, recoil, reorganization of my life," 17-year-old Alan Garcia told the class before breaking down in tears. "My mom goes in and out of recoil stage."
As the war enters its sixth year, it's bringing a new problem to Texas schools: Thousands of students suffering from emotional troubles not unlike those endured by soldiers returning from battle. In response, some districts have started offering the type of classes and counseling more common to the military.
"What you see happening in Iraq or Afghanistan is the same that's happening here in the border. This is not a war like those, but still you have people fleeing their country," said Clara Contreras, coordinator of the Safe and Drug-Free School and Communities program at the Texas Education Agency in Edinburg, Texas.
Many of the students were mugged or witnessed a shootout. Others have had family members kidnapped, or they have been extorted by gangs that run rampant in Juarez, a city of 1.3 million directly across the Rio Grande from El Paso.
As Garcia speaks, the class nods. Nearly all of the 17 kids with ties to Juarez have experienced the same anguish.
Kathy Ortega, director of counseling for the El Paso district, said officials do not keep track of how many students traumatized by border violence seek help, but the number includes both kids who have moved to Texas and others who still live in border cities but cross into the U.S. for school.
"Many of the families, because of the fear factor, won't reach out to us," Ortega said. Families are afraid that if their children speak with counselors, they could be identified by the people they escaped from.
Since the Mexican government launched an offensive on drug cartels in December 2006, more than 35,000 people have been killed in drug-related violence. The cartels' terror tactics include hanging people from bridges, beheading enemies and dissolving victims in acid.
Over that time, teachers and counselors on the Texas border have seen scores of traumatized children and teens.
The emotional difficulties affect them "in many areas of academic performance," said Alma Leal, professor of counseling at the University of Texas at Brownsville and coordinator for counseling and guidance of the Brownsville Independent School District. They suffer from poor discipline, lack any sense of security and fear losing loved ones.
Richard Barajas, a former chief justice for the Eighth District Court of Appeals, is director of advanced studies at Cathedral High School, where Garcia's class meets. He started teaching "Principles of Victimology" last year after two students were killed in Juarez.
The focus of the course is to teach students how to help victims, how to understand the process of victimization and how to talk about their experiences.
Mabel Avalos and other El Paso-area counselors have used skills they originally learned to help children of military personnel from nearby Fort Bliss.
Children fleeing from the cross-border violence and those whose parents have been in combat share issues like separation or loss of a parent, she said. But unlike military children, those coming from Mexico have sometimes been exposed to violence or been victims themselves.
"We tackle the problem, but we are not solving it," Avalos said. "I don't see the community realizing it's a problem."
She still has difficulty talking about how she had to explain to two siblings who had bullets lodged inside them why doctors refused to take out the slugs and instead waited for their bodies to push them out.
In Leal's district, counselors talk about how children fear for the safety of their relatives across the border in Mexico.
"I know of a teenager that crosses every day to see if his grandparents are still alive in Matamoros," just across the border from Brownsville, she said.
Susana Jones, a counselor in the El Paso area, said students who have been exposed to violence express their anger by fighting in school and talking back to teachers.
"After my brother escaped an attempted kidnapping, he started having anger issues. He would talk back to his teachers and eventually got expelled," recalls Carlos Gallardo, who graduated from Cathedral last summer.
When the two Cathedral students were gunned down in February, the slayings brought the cost of war back to the classroom.
"One of them sat right behind me, and it felt really weird whenever I'd look back and see the empty desk," said Carlos Gomez, a student who founded a group called Hope Without Borders, which focuses on raising awareness about violence affecting children and teenagers in general.
Many of the children were already struggling with poverty and now must confront "the overwhelming experiences of their worst nightmares and fears coming true," said Steven Marans, director of the National Center for Children Exposed to Violence at the Yale Child Study Center.
In the long term, if the children do not get help, victims can turn into victimizers.
"If you can't concentrate, and you can't do well in school, you can't find mastery in academics, so they find mastery using their strength" upon others, Marans said.
Victims in the drug war are often stigmatized by people who believe they had something to do with the drug trade.
In reality, said Laura Olague, executive director at the Children's Grief Center in El Paso, some of them were targeted for not paying extortion or got caught in the crossfire.
According to a study by the Geneva-based Internal Displacement Monitoring Centre, about 115,000 Mexicans have taken refuge in the United States since violence spiked in their country in 2006.