Patrons ride a roller coaster at Kings Dominion amusement park in Doswell, Va., in 2011. Because of a Virginia state code known as the “Kings Dominion law,” most state public school systems start classes after Labor Day, but with the holiday coming late in 2015 — on Sept. 7 — Prince William County has received a waiver to open schools on Aug. 31, 2015. (Linda Davidson/THE WASHINGTON POST)

While many children in Northern Virginia are lazing away the last days of summer next year, students in Prince William County will head to school before Labor Day for the first time, officials said.

The county School Board on Wednesday voted unanimously to approve a school calendar for the 2015-2016 academic year that has classes starting on Monday, Aug. 31. The decision will give students a two-week winter vacation, an earlier end to the academic year in June and more time for teachers to prepare students for standardized tests, according to a school system statement.

Traditionally, schools in Virginia begin in September immediately after the late summer holiday, part of a long-standing commitment to an obscure state code known colloquially as the “Kings Dominion law.”

Because Labor Day is on Sept. 7 in 2015 — the latest it can be in September — many schools in Virginia will begin on Tuesday, Sept. 8.

The 1986 legislation allows school districts to begin classes before Labor Day only if they receive a waiver from the state that takes into account the number of snow days from previous years. The law provides a late-summer boost to the state’s tourism and entertainment industry — including Virginia amusement parks such as Busch Gardens and Kings Dominion — by giving families one last long weekend hurrah before the start of school.

Prince William officials said the county received the waiver after canceling classes for 13 days because of inclement weather last winter, an unusually high number of closures that equaled nearly three weeks of school. It will be the first time that Prince William starts classes before Labor Day, spokeswoman Irene Cromer said.

Loudoun County schools also qualified for a waiver next fall, spokesman Wayde Byard said. It will be the eighth time in the past 16 years that classes in Loudoun will start before Labor Day, Byard said.

The new calendar in Prince William will not affect teacher contracts and will not add extra school days for students. The changes mean that classes next fall will begin only two days earlier than they did this year, when school opened on Sept. 2. The last day of school next academic year is scheduled for June 17, 2016, more than a week earlier than if the School Board had scheduled classes to start after Labor Day.

State officials in Maryland have sought to start classes after Labor Day in order to bring in more revenue from late-summer tourism. Many of Maryland’s 24 school districts start classes a week before Labor Day. A state task force recommended pushing the first day of classes until after the holiday, but teachers unions said the delay could affect training and class preparation for mandated tests.