MARION — On a recent sunny morning, Tabor Academy’s schooner glided through the calm waters of Sippican Harbor, making its way toward the open sea. With its soaring masts and intricate rigging, the vessel looked majestically antique — like a picture torn from a history textbook — as it cruised past the modern motorboats and sleek yachts bobbing on moorings in the harbor. Fifteen teenagers were aboard the schooner. They stood on deck, basking in the sunshine in their bright orange life vests, gripping a white cotton rope in their hands. Together, they worked like a team competing in a tug-of-war as they pulled the lines to set the schooner’s mighty sails.

Tamir Kalifa for The Boston Globe

Students climbed the foremast.

For this group of newly minted Tabor Academy students, it’s their first time sailing together, and it would not be their last. They were just beginning their Orientation at Sea, a weeklong sailing voyage on Tabor Academy’s beloved schooner, the SSV Tabor Boy.

The orientation sessions have been held for incoming students every week since the end of June. The last group of students to set sail this summer left this past Saturday and is scheduled to return Friday.

The nearly century-old schooner is something of an institution at Tabor, and it’s no wonder it holds an important place in the hearts of countless students and alumni. For many of them, it is their first introduction to life at the prestigious prep school known as “the school by the sea.”

Since Tabor Academy acquired the schooner in 1954, it has served as a sail training vessel, a floating classroom, science lab, and dormitory, all rolled into one.

The Orientation at Sea program started more than 20 years ago. Every summer since, nearly 100 incoming students participate. Many of them get hooked on sailing, and return to the Tabor Boy as a student crew member in the fall or spring.

“It’s an amazing program,” said John H. Quirk, the head of the school.

Students are taught the history of the nearly 93-foot-long schooner, built near Amsterdam in 1914 and originally called “Pilot Schooner #2.” It was used as a Dutch pilot vessel in the North Sea until 1929, and then served as a training ship for the Dutch merchant marine under a new name: Bestevaer. Years later, during World War II, Bestevaer was captured by the Germans and brought to the Baltic, and then ended up in the hands of the Russians. It was eventually recovered and in December 1946 returned to Rotterdam, where it was rebuilt and refurbished as a private yacht. In 1952, Ralph C. Allen, a businessman from Grand Rapids, Mich., brought the schooner to the United States and donated it to Tabor Academy two years later. It arrived in Sippican Harbor on May 20, 1954, and has been an integral part of Tabor ever since.

At the helm of the SSV Tabor Boy (SSV stands for “Sailing School Vessel”) today is James E. Geil, a longtime faculty member who goes by the nickname “Cap.” In his 26 years as Tabor Boy’s captain, Geil has logged more than 65,000 miles at sea and has sailed all over the coast of Maine, to the Panama Canal, and all the way down to the Caribbean Sea.

On a recent Monday morning, a group of new Tabor ninth- and 10th-graders — eight girls and seven boys — boarded the schooner and set off on their first day of sailing with some strict instructions. The 15 students could bring only one duffel bag full of necessities; they were not allowed to bring cellphones aboard. They had to leave their iPods behind, too. Just “traditional sailing and traditional communication,” said Emily Chandler, a science teacher who serves as the Orientation at Sea program director.

Tamir Kalifa for The Boston Globe

Brett Dineen climbed down the main mast of the Tabor Boy as part of an orientation session for incoming students at Tabor Academy.

The crew is made up of upperclassmen and recent graduates, who teach the newcomers the basics of sailing and navigation, and show them how to unfurl sails and handle the lines with finesse.

“We get them involved as much as we can,” said Chandler.

The program is optional and costs $650. But it has proved to be a wonderful opportunity for many students new to Tabor.

The private boarding school has a long history in Marion. It was founded in 1876 by Elizabeth Taber, a Marion native and wealthy widow who named the school after Mount Tabor in Israel. Sail training began at the school in 1918.

Today, Tabor enrolls 501 students from 20 states and 16 countries; more than 70 percent of them reside at the school. Tuition is $35,400 for day students and $49,400 for boarding students.

While not mandatory, all incoming students are encouraged to sign up for Orientation at Sea because, school officials say, it provides them a chance to get to know faculty and schoolmates before classes begin in the fall.

After the voyage, students receive half a semester’s credit in nautical science. They also finish with new friends and a better sense of Tabor’s 80-acre waterfront campus and the surrounding coastal area.

A typical day aboard the Tabor Boy begins at 6 a.m., with students doing three sets of pushups and jumping-jacks on deck. After their exercises, they usually take a quick dip in the ocean.

Breakfast is prepared by the ship’s official cook, Dutton Smith-Wellman, who is entering his senior year at Tabor this fall. He whips up blueberry and M&M pancakes, bacon and eggs, and makes sure the kitchen below deck is stocked with fruit, yogurt, Cheerios, Frosted Mini Wheats, Cap’n Crunch, and other cereals.

Besides the standard three meals a day, there’s also “Sierra Tango,” which, in the Tabor Boy crew’s maritime code, stands for “Snack Time.”

On their first day at sea, the students learned how to row a whaleboat, and they were shown how to prepare the Tabor Boy for sailing.

Tamir Kalifa for The Boston Globe

Students returned to the Tabor Boy after a lesson on a whaling boat.

Dave Griffin, one of the paid crew members, stopped to help one boy who was trying to wrap the extra line into a neat coil on the deck.

“Start right here; make sure you’re going clockwise,” said Griffin.

Not that long ago, Griffin was a fresh-faced student who didn’t know much about sailing. Now he’s a seasoned veteran and this is his third summer working aboard the Tabor Boy.

Griffin said Tabor introduced him to the world of sailing and life on the ocean. “I fell in love with it,” he said. He enrolled in the school’s Caribbean studies program, which gave him the opportunity to study in the Caribbean and sail back home on Tabor Boy.

“It was the most amazing thing I’ve ever done in my life,” said Griffin, who is from Duxbury.

Griffin graduated from Tabor in June and will attend Boston College this fall. He’s learned a lot from sailing — Tabor Boy “taught me to be responsible,” he said.

Over the next few days, the schooner would continue its sail to Hadley Harbor (near Woods Hole), Cuttyhunk Island, Penikese Island, and Vineyard Haven. Along the way, there would be lessons on geography, coastal marine science, the effects of salinity on the ocean, solar radiation, and answering such questions as why the ocean appears blue.

Tabor Boy has a website that is updated daily with photos and posts describing where the schooner has been and what the student crew did that day. It also tracks the ship’s current position and displays it on a map. To see where it is now, visit www.ssvtaborboy.org.