Initially Margaret Martin thought the want ad for a Cuttyhunk schoolteacher contained a typographical error. Scouring a jobs Web site for the Cape and Islands area in the spring of 2003, she saw an entry for a school with one student. She wasn’t reassured when she traveled to Rehoboth to meet Russell Latham, the district superintendent, and found that the listed address was actually a private residence. Sensing the whole thing might be an elaborate joke, she almost drove home to Long Island.

Cuttyhunk Elementary School is a single-room schoolhouse, built in the 1870s on one of a strip of islands a few miles to the northwest of the Vineyard which make up Gosnold. Cuttyhunk is the town’s municipal center and home to its only public school.

Since Ms. Martin, 28, arrived five years ago, school enrollment has doubled. Brittany Ann Doran, the school’s sole student when Ms. Martin took the job, has since been joined by her sister Casey. The girls are now in third and eighth grades.

On a recent Friday, the school was bustling. Cheryl McKenna, an art teacher from Plainville was on-island for the day, preschooler Carter Lynch had come in to do some reading, and Casey’s friend Sam was on a week-long exchange program. In the tiny, Cape-style building, there was hardly room to move.

Ms. Martin’s parsonage home is less than a hundred feet away, but in a sense it is all the way across town. On one side of the road the school, library, town hall and museum sit next to each other in a tight cluster. Opposite, the church completes the downtown area. Since the Doran girls live just a little further down the road, everyone leaves the school at midday to have lunch at home.

The forgiving commute is one payoff for living on an island which, particularly in the winter, can be brutal. In her first year there the harbor froze for weeks and Ms. Martin was faced with overdue bills and an empty fridge.

“I swore ‘I am getting off this island soon and I am never coming back,’ ” she recalled. “Most people can’t even fathom what I’m talking about when I describe my life. You couldn’t possibly believe it is accurate.”

But the school and its students have kept her here.

“It’s a lot to do with Brittany,” she said, sitting by the window in the reading corner of the schoolhouse. There is a clear bond between the two and Ms. Martin appears to move fluidly between the roles of teacher and counselor. “Not a lot of teachers have that with their kids,” she said. As she is keenly aware, it is also a responsibility.

“Here it’s just me and what they read is what they believe,” she said. “I have to chose every word carefully with them when I react to something in the news.”

Her job requires a knack for improvising and the skills of an all-rounder. The ferry schedule can make planning classes around materials difficult and it is often a case of make-do.

“If you’re not flexible it will drive you crazy,” she said.

For sports, the sisters run track by measuring the distance around one of the Island ponds. Because there are not enough numbers for a team, she coaches soccer skills. When the weather is unforgiving they learn yoga and pilates inside.

As a modern research facility, the town library has significant limits. In a recent attempt to use it for a project on Global Positioning Systems, Brittany got as close as a tome on early explorers and some writing on star astrolabes. Thus easy Internet access has proven a crucial educational tool.

“When I first got here we had dial-up wireless which cut out whenever a cloud went by too low,” Ms. Martin said. “We would wander around the classroom holding up the laptop looking for reception.” When a Verizon Wi-Fi tower went up on Cuttyhunk in 2003 it had a transformative effect at the school and allowed Ms. Martin to study for a master’s degree in curriculum instruction.

Though there have been more students in the past, they have rarely tipped half a dozen.

“We do everything that any other district does but it’s just tiny, it’s all in miniature,” said Gosnold superintendent Russell Latham.

While Vineyarders go off-Island, for example, the clipped Cuttyhunk version is simply “off.”

“The MCAS tests come in huge boxes and we only get one packet in those boxes. And from that we only need one test,” Ms. Martin said. Her task as proctor borders on the absurd.

“Students should be moved to separate areas when finished, cheating is strictly forbidden,” she said, reciting the language from memory, “Brittany is like, ‘Who am I going to cheat from?’ ”

The arrival of Casey in the classroom was a seismic shift from the first few years. “This was her sanctuary,” Ms. Martin said of Brittany. In an effort to maintain some of that structure, she extended her own working day by an hour to allow Brittany time to hand in her homework and prepare for the day before Casey arrives. The younger sister then stays behind half an hour at the end of the day.

Brittany is now contemplating a very different school experience. Having looked at several schools, including New Bedford High School, it appears likely that she will choose Bristol agricultural high school, where she is headed on Monday to take some class eligibility tests. Ms. Martin is pleased with the choice.

“My heart hurts when I think of her going [to New Bedford]. There are a lot of students with needs there ... someone like Brittany would just fall through the cracks. This school really helped her become who she is,” she said.

If Brittany herself is concerned about the change she doesn’t show it.

“I’m excited to be with other kids, I can’t wait to get to high school,” she said simply.

Brittany’s family will move to the mainland when she starts high school.

With Brittany and Casey moving on, Ms. Martin is eager to try something new.

“I feel like I’m ready to leave now,” she said. “I would like to teach a full class of kids, where they interact and there is peer review and discussion.”

Ms. Martin herself comes from graduating class of 700, in Smithfield, Long Island, one of the biggest high schools in the state at the time. Returning to Long Island for a year after college at Stonehill College, in Easton, she soon realized she was made for quieter climes.

“Long Island has a different energy. It’s just not me,” she said. She is concentrating her job search on Vermont. “I’m a basic person. I don’t mind mud on my shoes or not having Dunkin Donuts.”

Ms. Martin and the sisters make up the full-time faculty and student body of the Cuttyhunk school. With the three of them leaving, a mass walkout is in the offing.

But lean years are not uncommon at the Cuttyhunk school. “We’ve had to close the school a few times,” said Mr. Latham, who describes years where the island has literally been without a child. But since a daily off-Island commute is too much to expect of elementary school kids and home tuition actually constitutes private schooling, the school institution has to remain, as long as Cuttyhunk is inhabited.

“Gosnold is obligated to a provide a public education option,” Mr. Latham said, as if the words are issued direct from Capitol Hill.

There are four children of preschool age currently on Cuttyhunk, two of whom are already being taught part-time at the schoolhouse. Mr. Latham predicts that the school will morph into a part time early-learning center in the next few years and gradually reform as a full-time elementary.

However it works out, the survival of Cuttyhunk Elementary School is beyond doubt.