Schools Superintendent Pat Hamamoto said the common schedule should make it easier for students who have been on different schedules to participate in activities together outside school, and should make it more convenient for families to plan vacations. The change also is meant to facilitate teacher training.

"What we hope to accomplish with the single calendar is to improve the quality of life for families and the community," Hamamoto said. "It will help the school community, and the community at large, know when to plan activities that impact families and involve kids."

The new calendar also is expected to save money on operating school buses and providing meals, and by consolidating contracts for other services, she said.

About 100 schools operate on a traditional nine-month calendar, but more than 170 others follow a year-round or modified schedule.

Schools began diverging from a common calendar more than 10 years ago, when some decision-making power was shifted to individual schools and communities.

Public charter schools would not be bound by the new schedule, nor would four regular schools that operate on multi-track calendars: Holomua Elementary, Kapolei Elementary, Kapolei Middle and Mililani Middle.

The proposed schedule was not the most popular of five options presented last year in a survey of more than 126,000 parents, students and state education employees, according to a report prepared for the board.

But other choices tended to draw a polarized response, with a high percentage of people strongly opposing a calendar that many others favored, officials said.