The start of the 2017-18 academic year in public schools across Long Island rolls out on seven separate days, from the earliest on Aug. 29 in the Jericho district to the latest on Sept. 7 in five systems — one in Nassau County and four in Suffolk.

The staggered nature of students’ back-to-school days is typical for the Island, driven by when Labor Day falls, holidays built into the school calendar, and whether teacher unions in individual districts adhere to contracts specifying that classes begin after Labor Day.

This year, the span from earliest to latest occurs over a broad 10-day range.

The two days after Labor Day will see the bulk of openings.

Sept. 5 is the day that the greatest number of districts will begin holding classes, as 36 systems start in Nassau and 34 open in Suffolk. The second most popular day is Sept. 6, with 14 districts opening in Nassau and 30 in Suffolk.

The state Education Department requires at last 180 days of classroom instruction. Districts can choose to add to that, and some on the Island do.

advertisement | advertise on newsday

The Jericho system, a perennial early starter, this year opted for 184 instructional days for students and two so-called superintendent’s conference days for staff development, training and other matters.

“Jericho has almost always started school before Labor Day, in order to get the 186 days,” said Superintendent Henry Grishman, noting this has been the practice for two decades. “We believe that is better — longer school day, longer school year. This philosophy provides more instructional time, which our school community believes benefits our students.”

The other districts opening before Labor Day are Great Neck, Herricks, Oyster Bay-East Norwich and Westbury.

In Herricks, where classes start on Aug. 30, the traditional opening has varied — sometimes before Labor Day and sometimes after, district spokesman Michael Ganci said. This year, the system has 181 instructional days and four superintendent’s conference days.

Herricks’ 2017-18 calendar includes more holidays, with school closings for the Muslim festivals of Eid al-Adha later this month and Eid al-Fitr in June, the Hindu observance of Diwali in November and the Lunar New Year in February.

Those observances are in addition to federal holidays and the longstanding traditional breaks for Rosh Hashanah in September, Thanksgiving in November, the winter recess that covers Christmas and New Year’s, and the spring recess that will include Passover, Good Friday and Easter. This year, Yom Kippur — the Day of Atonement for those of the Jewish faith — begins at sundown on Sept. 29, a Friday, so most public schools will be open during the day.

Laura Seinfeld, superintendent of the Oyster Bay-East Norwich schools, said the district decided to start classes on Aug. 31 rather than the typical Sept. 1 opening. The system will have 183 instructional days and two for professional development.

“We built in two superintendent’s conference days, because these days are important team- and skill-building opportunities for our faculty that reinforce district goals,” she said.

Middle Country is a school district that is following suit with most public schools on Long Island, starting after Labor Day. The large Suffolk County system will begin classes on Sept. 6.

Superintendent Roberta Gerold said the timing is normal for the system, which will have 180 instructional days and two staff-development days.

advertisement | advertise on newsday

The district’s teacher contract has a clause saying that teachers cannot start before Labor Day, Gerold said. Over the past five years, however, the staff has been cooperative and willing to come in before Labor Day to make sure they hit the goal of 180 instructional days, she said.

The five districts with the latest openings — on Sept. 7 — are Elmont in Nassau County and Babylon, Connetquot, Shoreham-Wading River and Smithtown in Suffolk.

Shoreham-Wading River’s later start is tied to summer construction projects at Wading River Elementary School and Miller Avenue Elementary School. While the projects are on schedule, the district allotted an extra day in case more time is needed, spokeswoman Deirdre Gilligan said.

Most Catholic elementary and secondary schools will start classes on the Tuesday or Wednesday after Labor Day, diocesan and school officials said.

For example, the two high schools run by the Marianist brothers start on different days — Kellenberg Memorial High School in Uniondale on Sept. 5 and Chaminade High School in Mineola on Sept. 6.

advertisement | advertise on newsday

With Bart Jones