Visit to a one-room schoolhouse. The desks may be old-fashioned, but the computers are up to date

SAGAPONACK (population: 361) is a hamlet southeast and seaward from Bridgehampton on Long Island. Technically, Sagaponack and Bridgehampton are part of Southampton -- The Hamptons, as they're occasionally referred to, the much-touted summer spa. True to Yankee form, though, Sagaponack has a rock-ribbed penchant for home rule. Sagaponack School is this penchant made manifest. On a 1986-87 budget of $99,000, the neighborhood is educating its 15 first through fourth-graders. Enrollment here, one of three one-room schoolhouses in New York, has altered little since the first class on Caleb Pierson's property in 1776.

As Southampton town historian Robert Keene explains, there is a lingering New England aura to outermost Long Island. The region's first settlers were kinsmen of New England's settlers -- Long Island is just 16 miles from the shores of New England, Mr. Keene relates in telltale Yankee chant.

Development has been displacing local agriculture. While cornfields still abut the school, all around is evidence of transition. Classifieds in the local press are chock-full of land sales. Scuttlebutt at Sagaponack's post office (the size of a butler's pantry) concerns a local elder who just sold a tract.

But as of yore, three trustees and a part-time superintendent hire one teacher who serves as instructor, building principal, and secretary, not to mention nurse, electrician, and plumber as circumstances demand. Regina Guyer presently wears these hats.

The school has a pot-bellied stove, and antique desks with tendril-like wrought-iron legs. There is a bell in the cupola that one fourth-grader or two first-graders ring daily at dismissal.

Not all is throwback, though. In a bow to modernity, Sagaponack also has one Apple II and one Commodore personal computer, as well as a Xerox machine that huddles like a mascot pachyderm in a tiny anteroom.

On a typical day, students rotate from ``subject center'' to ``subject center'' around the main room. Grade levels are mixed at each center. Erin Thayer, an elfin seven-year-old, is content with the system. ``I love the school,'' she says, ``because we get to learn from each other.''

Ultimately, students here take the same Stanford Achievement, Gates, and Metropolitan Reading tests taken by students in most standard New York classrooms. ``We're fully accountable,'' Mrs. Guyer says. The school consistently scores above average. ``They get a solid background, simply because I've got time to spend with each of them.''

Alumni grant that going from Sagaponack to fifth grade at another school was a culture shock. Still, there are few regrets. Frank H. Tillotson, who started at Sagaponack (or Sagg School, as it is also known) in 1922, contributed this entry to a recent alumni scrapbook: ``I think it's a wonderful, historic occurrence that Sagg School still exists today. And I hope, considering the superior learning which results from the school, that it continues for a long time. Fight like mad to keep it.''

On those same pages, alumnus Charles (Berkley) Parker recalls a day in the 1930s when class was let out early because Mrs. Stewart's pig was loose in the yard. The Saggs, it seems, agreed it would be nothing short of a civics exercise to bring home home the bacon.

As she dismisses class at 3 p.m., Regina Guyer muses, ``I left a tenured position in Montauk [N.Y.] to come here. If you're not challenged as a teacher, you're not fresh.''

There is a silent interval. The neighborhood hush is ruptured only by the purr-and-squeak of a passing potato truck, the fall thrum of katydids, a wheeze of distant saws.

``Sagaponack School will be here until there are no more children to come to the school,'' the teacher resumes and concludes.