Students change classrooms during a break at the International Academy of T.C. Williams High School in Alexandria. (Astrid Riecken/ The Washington Post)

Lisa Haskins was trying to explain the concepts of theme and plot to a dozen fidgety adolescents. Most of those in her class at the International Academy in Alexandria spoke little or no English. Some had been in the United States only a few months.

To bring the lesson closer to home, Haskins handed out a short story about a Mexican family trying to flee across the U.S. border.

Several students stared blankly, so Haskins changed tactics.

“Manuel, please read and translate for us,” she asked.

A quiet Central American boy straightened up and cleared his throat. He stumbled through some sentences, mispronouncing “guard” and “fence,” but his voice gained confidence as he continued.

Susannah Courand, International Academy department chairwoman, assists during a biology class for students at the International Academy of T.C. Williams High School in Alexandria. (Astrid Riecken/The Washington Post)

“We crawled under the fence,” Manuel read.

The girl next to him, who had recently arrived from Mexico, smiled politely but understood nothing.

Manuel switched to Spanish, and she began to nod.

“How do you say ‘crawl’ in Spanish?” he asked.

“Gatearse,” an older student answered.

Suddenly, the girl’s face lit up with recognition.

By the idealistic standards of the International Academy, an experimental high school program for young immigrants who do not speak English, Haskins’s class that fall morning was a success. A second-year student with limited skills had helped a new classmate who had none, building his own self-esteem and drawing her into a friendly learning environment.

Math teacher Katrina Deady teaches immigrant students at the International Academy of T.C. Williams High School in Alexandria. (Astrid Riecken/The Washington Post)

But the surge of nearly 3,000 unaccompanied minors who have reached the Washington area from the border this year — including 150 enrolled in the Alexandria academy, located on the third floor of T.C. Williams High School — has put unprecedented strains on its staff, facilities and unique educational philosophy.

The international high school model was founded in New York City in the 1980s, during a soaring influx of Spanish-speaking immigrants. Its mission is to integrate foreign youths into U.S. society, teach them basic English and give them a solid high school education, all at the same time.

Its methods are un­or­tho­dox. Students of different ages and grade levels take the same classes in all subjects, and the more advanced ones are expected to help the newcomers. Teachers volunteer for the program and are trained to work in teams; counseling sessions are held often.

Today, there are 19 such schools nationwide, mostly in New York and California. The Alexandria academy opened in 2011, another started last month at Cardozo High School in the District, and two more are expected to open next fall in Prince George’s County through a partnership with the immigrant advocacy group Casa de Maryland.

Kenji Hakuta, a Stanford University professor who specializes in English-language learning, said the international high schools have been successful in part because they demand “a high expectation of rigor” from students while offering them extra emotional and academic support.

“I admire them and I think they are doing a very good job,” he said.

According to officials from the Internationals Network for Public Schools, a nonprofit organization that sets up each school, their students complete 12th grade at two times the rate of similar new immigrants at regular public schools.

“We encourage them to be teachers as well as students, because it empowers them and helps them learn to think critically and collaboratively,” said Claire Sylvan, the founding director of the Internationals Network. “We are trying to do in one generation what normally takes three.”

No one, however, was prepared for the surge of 2014.

Each morning for the first few weeks of school, a new batch of nervous Latino teenagers were ushered into the office of Danielle Wierzbicki, the Alexandria academy director, for orientation. Almost all had been detained at the U.S. border and released to relatives; the Washington area received the fifth-highest number among all U.S. urban areas.

By October, total academy enrollment had swelled to 590, and some classes had grown from 18 to 25 or 30 students, leaving Wierzbicki and her staff scrambling to find extra desks and juggle teachers’ schedules. About 75 percent of students are Hispanic; the rest are from the Middle East, Africa and Asia.

During several weeks during the fall semester, a Washington Post reporter visited the program a dozen times. School officials asked that no minors be identified and that no student’s legal status be mentioned, but it was easy to pick out the struggling newcomers and watch their progress.

Day after day, bewildered children from El Salvador, Honduras and Guatemala sat through a blur of fast-paced math and biology classes. All were assigned seats next to older pupils, who helped them translate texts and instructions. A few caught on quickly, but others seemed so lost that it was hard to imagine how, in just eight months, they could pass the standardized tests in English required to move up a grade.

At the same time, academy staffers said controversy about the surge of Central American minors had spurred resentment among some members of the school system, who complained that scarce resources were going to youths who had entered the country illegally.

But Alexandria school officials said the academy costs are met entirely from regular public education funds, plus an extra amount the federal government allots annually for every student designated an “English Language Learner,” no matter what public school they attend.

Last year, Alexandria had 3,243 such English learners enrolled in its schools, including several hundred at the academy, and received $361,900 in federal funds to support them. This year, the number of students rose to 4,019 and the federal allotment was $434,000.

“Some outsiders may be a little resentful, but I shudder to think what would have happened if we didn’t have this program now,”said Susan Maxey, the principal of T.C. Williams. “It makes their transition so much easier. Other schools are struggling with the influx, but we have made it work. Our challenge is to make the rest of the school community appreciate what is going on here.”

The Alexandria academy, which opened with only a ninth grade, has not yet held a graduation. Its stars are the 130 juniors who made it through two academic years and now speak English with ease. Academy officials said their 6.6 percent dropout rate is much lower than the statewide average of 21 percent.

Derlin Castillo, 20, a junior from El Salvador, is a math whiz who speaks excellent English and works evenings in a restaurant. “I am tired all the time, but I love school,” said Castillo, whose goal is to become a physician’s assistant.

Wierzbicki said when students drop out, it is usually because they have to earn money or babysit at home. She said school counselors work with churches and nonprofit groups to help them with rent, child care and even to pay debts to guides who charge several thousand dollars to ferry minors to the U.S. border.

Many of the newcomers, staff members said, are grappling with personal difficulties at home, especially adjusting to new lives with parents they have not seen in years. The school offers them frequent group “advisory” sessions, where they are encouraged to express their feelings, and private access to Spanish-speaking counselors.

“They have come to live with people who abandoned them, after long separations. They feel the wounds, sometimes even the hate,” said David Wynne, the academy’s social worker. “You never know what issues can spring up from the past. They show up at my door in tears, and I don’t know where to start.”

Even before the surge, teachers at the academy faced another problem: tension between the twin goals of keeping up a fast, test-oriented academic pace and slowing down for stragglers with poor English skills. Now, the crush of newcomers has added to that tension.

In Kirsten von Topel’s English class, students were assigned one day to read a story called “The Sniper.” It was about a militiaman on a rooftop in Ireland who shoots and kills an enemy fighter on another roof. In the final sentence, the man discovers he has killed his own brother.

As the students neared the end of the tale, a 10th-grade girl from Peru gasped aloud. Several Central American students whispered to each other in Spanish and finally understood.

It was a moment to reflect on life and war and the power of words. But von Topel had little time left — and a list of required literary concepts to drill into 20 heads.

“Okay, let’s go over it again. What is the climax of the story? . . . Who is the protagonist?” she asked briskly, waving her arms. “What is the voice? It is limited or omniscient? . . . What is foreshadowing? Where do we see it? In the title!”

As the bell rang, a Salvadoran boy yawned and leaned over to the Peruvian girl. “What does the title mean?” he asked in Spanish.

Others made steady progress, even in subjects like biology where they were bombarded with new scientific terms. They seemed to do especially well when they took advantage of older students’ knowledge.

One girl from Guatemala, who arrived in May speaking no English, learned the word “rabbit” during her first day of school. Two weeks later, her biology teacher asked everyone for examples of how living creatures use natural resources.

The girl, seated next to a 10th-grade boy from Honduras, asked him to translate the question. She thought for a moment and wrote, “rabbit eat. . . .” Then she frowned and asked her neighbor for help once more.

“Rabbit eat grass,” she wrote.