One morning before math, the fourth-graders took a little vacation. To soft music, they walked through woods, climbed a mountain and lifted off with imaginary wings, flying over an ocean, a gentle breeze on their faces. One student saw a school of fish; another spotted a rainbow.

“I see it!” the others piped in, their eyes squeezed tight. “I see it, too!”

With the sound of a chime, they were back in their yellow-and-blue school uniforms in a classroom overlooking a blighted neighborhood that has been beset by violence this spring, including two separate slayings of teenage boys at a nearby Metro station.

Like a growing number of schools nationwide, Houston Elementary in Northeast Washington is using mindfulness and other therapies to help children manage the stress they encounter in their daily lives.

Akilah Foster takes her children, Jeremiah, 6, and Nariyah, 3, to Houston Elementary. The family is living in a hotel room. (Bonnie Jo Mount/The Washington Post)

Neurological research shows that traumatic experiences such as being abused, witnessing a violent crime or even living in a neighborhood where crime is pervasive can transform the developing brain. They alter the chemical balance, making it more difficult for children to concentrate, create memories and build trusting relationships — all fundamental skills for performing well in school.

The research is motivating educators to rethink zero-tolerance discipline policies that punish kids for outbursts that can be signs of trauma and to rally support for efforts to bring more mental health care into schools, where students and families have ready access to them.

“The brain cannot focus when it’s not calm,” said Susan Cole, a Harvard Law School professor and director of the Trauma and Learning Policy Initiative, which advocates for “trauma sensitive” schools. “Children have to feel safe enough to learn.”

[“Toxic stress” in the classroom: How a public-health approach could help]

After eight years of intensive reforms, an infusion of new teachers and an overhauled curriculum, academic performance remains very low in dozens of the District’s schools, mostly in parts of the city where children are the most vulnerable. At Houston, 5 percent of students met grade-level expectations last spring on new math tests, and 1 percent performed at grade level in reading.

D.C. Council member David Grosso (I-At Large), chairman of the education committee, said trauma is a “root cause” of the achievement gap between rich and poor students, and he aims to shepherd more resources for mental health services in public schools. Services vary widely, and the city is assessing what is available school by school.

San Francisco has been using a “trauma-sensitive” approach since 2008, including training for students, their parents or caregivers, and school staff. This year, Boston received a federal grant to hire trauma specialists to work in 10 public schools.

Justice Douglass meditates during a class at Houston Elementary. (Bonnie Jo Mount/Washington Post)

At a town hall meeting this month, Houston Principal Rembert Seaward asked the students gathered in the cafeteria how many knew someone who had been shot. More than half of the children raised their hands. Anxiety has been running high in the neighborhood in recent months since one teenager was shot and killed at the Deanwood Metro station and another was fatally stabbed there two weeks later.

“It’s been shooting after shooting after shooting,” said Denise Robinson, a Houston mother.

She tells her second-grade son, Tevin, that the noises outside his window are fireworks, but he hears the sirens and is often anxious and worried about his family’s safety.

He doesn’t like to go outside and he clings to her when she gets ready to leave, she said. Some days, he resists going to school. “He thinks he’s not coming home,” she said.

Excessive stress can have lasting effects. A landmark study in 1998 involving 17,000 adult patients from Kaiser Permanente found that those who had experienced more adversity in childhood, through experiences such as having a parent with mental illness or drug addiction, were far more likely to suffer from poor health later in life, including depression, heart disease, obesity and cancer.

Adverse experiences are common in the general population, with about two-thirds of those surveyed having at least one. But they are far more common in poor neighborhoods such as Deanwood.

When Seaward came to Houston three years ago, he was struck by the level of stress he found at the school.

“The kids here, something was different,” he said. “They did not seem like children. They seemed like they had to grow up quick.”

Stress has many sources for Houston families. There are stresses associated with being a teenage parent or living with three generations in a one-bedroom apartment or having a parent incarcerated.

For Akilah Foster and her two young children, stress is waking up at a hotel in Maryland and taking three buses and a Metro train to get to school because they are homeless.

Losing her apartment last winter sparked a fighting instinct in Foster. The 23-year-old mother sought help from the school to find housing. She kept her son in after-school football to maintain a steady schedule when they were staying with friends and relatives. And she re-enrolled in school after she quit her restaurant job in Virginia because she did not have reliable transportation.

Some other families retreat under pressure, dogged by depression or drugs. They keep the doors closed when social workers from school come knocking.

In an effort to help all families and their children cope, Houston contracted last year with Turnaround for Children, a group that works to make schools more responsive to children affected by trauma.

The organization was founded by Pamela Cantor, a child psychiatrist who conducted a major study about the traumatic effects of the Sept. 11, 2001, terror attacks among students at New York public schools. She found the most profound symptoms of post-traumatic stress were not in the neighborhoods surrounding Ground Zero, but in the poorest pockets of the city.

“We observed that poverty itself was an adversity in children’s lives, a trauma,” Cantor said.

In an initial meeting, Seaward brought a list of 34 students — more than 10 percent of the school’s enrollment — who he thought had acute mental health needs.

This year, Turnaround brought in an outside mental health provider, including an additional social worker who has a full caseload of 20 families.

An instructional coach trained teachers about toxic stress and how the same heart-thumping surge of adrenaline that can save a life also can cause children to lash out at seemingly minor provocations.

In weekly sessions, teachers practiced setting clear expectations and maintaining a calm classroom and demeanor. The goal is to limit disruptions and de-escalate conflicts to give students a chance to learn to calm down.

School suspensions have been reduced significantly in the first year of the partnership, from 76 last year to 19 this year, and a survey showed dramatic improvements in how school staffers perceive the school’s climate. Last spring, just a third of employees said they thought students felt physically safe in the building, compared with 94 percent this spring.

Experts say children can recover from adversity, particularly when they have an adult they can trust to help them manage the stress.

At Houston, that person for many children is Darryl Webster, the school’s social worker.

Webster is 6-foot-6, generous with hugs and kind words, and he is busy from the moment he steps into the school. He is the person who responds if a student has missed class or arrived with a bruise on his face or a burn on his arm. He talks to students about the risks of sexting or using drugs, and he explains how to process feelings about the killings in their neighborhood.

One colleague called him the “Pied Piper,” for the trail of children following him down the hall. They bring notes from teachers if they are disrupting class, details of a nightmare they had, a longing to be near him.

[Read about Darryl Webster’s early career as a social worker in this two-part profile here and here]

D.C. Public Schools is investing in more training and strategies to respond to trauma, Webster said.

Webster has started a grief and trauma counseling group for children who have lost relatives, including several children whose loved ones were killed. He also conducts play therapy, which helps children process feelings they have a hard time addressing.

On a recent morning, Webster got a second-grader out of class who was depressed and not talking. They walked upstairs to a room full of toys. The boy picked out a board game, and the two sat on the floor and played until he was relaxed and smiling. Later, the student went to a table stocked with toy figures, and he picked out a pretend hypodermic needle and two cigarettes. He brought them over to the sand table, took out a plastic shovel and buried them in the sand.

Another day, Webster led four squirming little boys toting yoga mats into the library for a meditation session.

“This is the only free, easy thing I can give them,” he said. “It gives them some control over their minds and bodies and things they feel they don’t have control over.”

They giggled at the New Age music on his cellphone, did somersaults and tried to roll themselves up in the mats.

Eight-year-old Tevin was there, the only one who was still and listening as Webster told the group to let go of their worries and fears and concentrate on their breathing.

Webster asked how he was feeling. “Happy,” Tevin said.

He turned his face to the wall and closed his eyes, while Webster continued: “We are on a mountain. It’s a beautiful sunny day. Now take out your wings and fly.”