Thanksgiving break will start two days early at the Tisbury School, where an $82 million renovation and addition project is about to ramp up.

Over the weekend of Nov. 19 and Nov. 20, Carroll Movers will empty the school, school committee chair Amy Houghton said Monday at a joint meeting with the school building committee and Tisbury select board.

Much of the classroom contents are destined for the new modular facility on the West William street side of campus, where school resumes after vacation on Nov. 28, but principal John Custer said the rooms won’t be ready for students and teachers until then.

“It is unfortunate,” Mr. Custer said, acknowledging the inconvenience to working parents who had expected Thanksgiving break to start Nov. 23, not Nov. 21.

“To be prepared to safely and appropriately receive students on the 28th, we need that time,” the principal said. “We’re hopeful that folks are understanding.”

Owner’s project manager Mike Owen of CHA apologized to the school community for the early move, but said the timing was essential.

“We have a hard date,” Mr. Owen said. “We’ve got to turn the building over Dec. 1 to the construction manager to stay on schedule.”

Rita Jeffers, a teacher and member of the committee, said school staffers are scrambling to find safe, supervised alternatives for children on Nov. 21 and Nov. 22.

“People are working feverishly behind the scenes to figure out coverage for kids,” Ms. Jeffers said. “We have lots of working parents.”

By contract, teachers cannot be required to do any work on the dropped class days, Ms. Houghton said.

“That’s not something we can do,” Ms. Houghton said, adding that teachers are eligible for up to eight hours’ moving pay.

The school committee voted unanimously in favor of the schedule change, which Mr. Custer said the state education commissioner has approved as long as the two days are made up at the end of the school year.

Meanwhile, as the modular school nears completion, a temporary cafeteria is in the works across West William street at American Legion Post 257, which is leasing its kitchen and dining area for school use during the construction project.

School committee members are working with the Legion, Tisbury building commissioner Ross Seavey and town health agent Maura Valley on reconfiguring the space for school meals, Ms. Houghton said.

Committee members approved up to $50,000 from the school’s $373,000 school choice fund to pay for the updates, including fresh paint.

At the committee’s request, the select board agreed to make West William a one-way street, eastbound toward Look street, to make it safer for children crossing for lunch at the Legion.

Either an eastbound or a westbound pattern would be equally safe for children on foot, Tisbury police chief Christopher Habekost said, but parental vehicles are another matter.

At school pick-up and drop-off times, Chief Habekost said, westbound traffic could back up to the heavily-used juncture of Look street, State Road and Edgartown-Vineyard Haven Road.

About 100 families regularly drop their children off and pick them up by automobile, Mr. Custer said.

The eastbound-only traffic pattern on West William is expected to remain in effect from September to June until the building project is completed.