OAKLAND — Three months after President Barack Obama declared their mass arrival an “urgent humanitarian situation,” thousands of children who fled Central America are about to take a seat in U.S. classrooms for the first time.

Some Bay Area schools are bracing for an influx. Others don’t know what to expect or haven’t thought about it. The Oakland Unified School District, more prepared than most, is anticipating so many newcomers that it is hiring a privately-funded consultant to cushion their landing.

“Moving anywhere is one of the most stressful things any kid can do. Compound that with moving countries, moving cultures,” said Carmelita Reyes, co-principal of Oakland International High School. “It’s the most stressful situation. And you’re 15. It’s incredibly hard.”

Many are landing in cities that already had a large Central American community, such as Oakland, San Francisco, Richmond, Concord and Redwood City.

More than 340 recently arrived immigrant students from Guatemala, El Salvador and Honduras have enrolled in Oakland schools since last summer. At least 150 are known to have crossed the southwest U.S. border unaccompanied by parents or guardians and now await hearings in immigration courts. Some are already known to teachers, but many arrived just a few weeks ago after school let out for the summer.

Reyes is accustomed to helping high school students navigate a new world. Her school in North Oakland’s Temescal neighborhood educates immigrant students from around the globe.

But the newly arrived Central American students, along with confronting the challenges of learning English and overcoming trauma, have additional difficulties that most newcomers do not encounter.

“Imagine being 15 and being told you need a lawyer, in a country where you don’t speak the language and have no money,” Reyes said.

Teachers say legal complications are one of the biggest distractions for the new students, most of whom are in deportation proceedings but seeking asylum or other permanent protection after fleeing violence in their home countries. Unlike indigent criminal defendants, they don’t qualify for free legal representation. And unlike legally-recognized refugees who are paired with case workers, they may not qualify for health care, welfare benefits or other federal help.

Compounding these difficulties are precarious living conditions where some students feel that they “are being a burden on the household,” Reyes said. The federal government, after detaining the children at the border, has kept some in youth shelters but released most to relatives or family friends. Often the relative is a parent, but Reyes said sometimes it’s a distant relative or even an adult brother or sister.

“If a kid gets in trouble, and you call home, you’re talking to a 19-year-old,” Reyes said. “A lot of 19-year-olds are not in an economic or social situation to take care of a minor.”

A group of educators at Oakland International High appealed for help this summer after the school took in about 50 unaccompanied migrant teenagers in the past year, about an eighth of the school’s population. Many of those students returned for a summer session that ended on Aug. 1.

Fremont High School in East Oakland also enrolled a large group of Central American students, as did Bret Harte Middle School.

“Students who were unaccompanied were missing class and not performing as well,” said Nate Dunstan, the school district’s point-person for refugee students. “They were so preoccupied with the other things going on in their life, primarily legal stuff, but also health and mental health.”

Oakland’s Board of Education is expected to vote Wednesday evening to accept $45,000 from the San Francisco-based Zellerbach Family Foundation and $30,000 from the Moraga-based Y&H Soda Foundation. The money will be used to hire an “unaccompanied minor specialist” and provide related services to track down the students and monitor how they are adjusting.

The San Francisco Unified School District said Tuesday it plans to hire another two to three high school teachers this fall to accommodate more than 200 newly arrived Central American students who have already enrolled this year, in addition to 422 who had enrolled last year.

In Contra Costa County, the West Contra Costa district is working with Catholic Charities to enroll 64 unaccompanied migrant students from Central America in adult education programs, some elementary schools and Kennedy and Richmond high schools. The high schools offer health and dental clinics, mental health counselors and connections with social services agencies and nonprofit groups, said district spokesman Marcus Walton.

Jeanne Alessandra Duarte, director of English Learner Services at the Mt. Diablo school district, said 19 new Spanish-speaking immigrants have so far enrolled in district middle and high schools. Although she said the district could not say specifically which countries they are from, she said, in general, the district has seen an influx in students from El Salvador since January, mainly 15-17-year-old males.

“It’s obvious that they were coming from a war-ravaged country, in terms of what we’re hearing now in the news,” she said.” We didn’t know why there was such a large number, but now it makes sense.”

The district provides services to some unaccompanied migrant students through its homeless outreach program, said Administrator James Wogan. The program provides free school meals and helps students find food, clothing, shelter and access to health and dental care.

Wogan said most of the students have someone helping them get to school.

“To make it this far north, often they’ve had some adult, agency, or other person involved in helping them to find their way here and they’re coming for some stability in their lives,” he said.

The number of children illegally crossing the border began tapering down in July, but more than 62,000 arrived unaccompanied since October, according to government data. California has taken in more than 3,900 since January, the third-largest group after Texas and New York.

Staff writer Theresa Harrington contributed to this report. Contact Matt O’Brien at 510-208-6429.