As students, they took turns on the schoolhouse roof searching the skies for suspicious aircraft, while Army troops convoyed down Main Street. School House Pond behind the building was for skating. Parents coming to school meant only trouble.

This was the world of white Upper Marlboro more than half a century ago, a time that seems so distant. But to the aging graduates gathered in front of their old elementary and high school building Saturday, it was as if it were only yesterday.

"Here we received the best of the best," said Helen Hall Ford, of the Class of 1945. It was an education that emphasized "high moral standards, love for our country, personal responsibility, that have anchored us in a lifetime of . . . experiences," Hall said.

To mark the spot where many of the children of Marlboro were educated for 150 years, the group Saturday dedicated a plaque affixed to a 6,000-pound rock on the rise across from the post office. The school is long gone; the brick building now houses the office of the Prince George's County sheriff.

For the 75 graduates who gathered in the winter chill, it was a time for emotion and humor. The Rev. Edward "Pete" Dorsey (Class of 1941), about to deliver the invocation, recalled a stern principal. "I'm sure Wilbur Jones never thought I'd be standing here doing this," he deadpanned.

The graduates were all white, because racial segregation also was part of the fabric of life in Prince George's until the not-so-distant past.

The old Douglass High, for blacks, which was also in Upper Marlboro, was razed years ago. The courthouse garage is at that site.

The bronze plaque commemorating the Upper Marlboro school doesn't mention this aspect of school or much else but basic dates and facts. It barely begins to tell the story of what life was like for these Upper Marlboro High School graduates, most of them in their 70s.

It was a time when only 100,000 people lived in the county, whose population now approaches 800,000, when there were nine high schools for whites and two for blacks in all of Prince George's--compared with 22 today--and some, like Marlboro, included first through seventh grades as well.

For the plaque and boulder, the graduates raised $4,000, more than enough. The rock was placed there in October, but the dedication was postponed until this weekend, after the holidays.

Despite the demographic changes, many of the graduates remain in the area. Within the 284-acre town, moreover, they still have political clout, recently helping to reelect Helen Hall Ford to another term as president of the Upper Marlboro town commissioners.

They came from "town," as Upper Marlboro was known, and from settlements and schools long gone or mostly forgotten, such as Meadows, Mullikan, Ritchie, Nottingham, Naylor.

Their names are a who's who of who was and still is--local families with deep roots: Buck, Wyvill, Chaney, Beall, Baden, Moore, Pumphrey, Tippett, Wells, Hall, among others. Several continue to see each other. Ten to 15 people from the Class of 1946 meet for lunch every three months, often at Rip's, on Route 301 in Bowie.

Many came off the farms, where invariably the cash crop was tobacco. Not a few were the sons and daughters of sharecroppers kept home from school during harvesting in September and planting in the spring, the boys often dropping out before graduation.

"I had to work from sunup to sundown, whether I went to school or not," said Gilbert E. Moore, a 1947 graduate who lives on a remnant of his father's farm on Melwood Road. Back then, the family had neither running water nor electricity. He aspired to be a bookkeeper but, after a few years of farming, began to sell insurance.

Lewis B. Dodd, the son of a Glenn Dale sharecropper, finished school in the middle of the school year, in February 1946. Until then, he had to walk a mile to catch the school bus to Marlboro. "I think we started as freshmen with 125 in our class, ended up at graduation with 41. The rest dropped out, went back to the farm."

Dodd graduated from high school and went directly into the Army--his yearbook ambition--and served in occupied Japan. He later moved to Bowie and was a road contractor. One senior boy said he hoped to become a tobacco merchant. Many of the boys went to work for the telephone company.

The school served a region that was nearly half the county, from Glenn Dale to Forestville to Brandywine. But its graduating classes were small: 31 in 1941, 28 in 1945, 41 in 1946--including 26 girls, 15 of whom aspired to be secretaries or typists.

Anna LeBark Prout went right to work for the Farmers and Merchants Bank of Upper Marlboro, retiring after five bank name changes as head teller at the Census Bureau branch.

"Not many went to college," said Rose Goen Hoffman (Class of 1941), who got a government secretarial job and still lives close by. "More often [the boys went into] the service. We didn't have many guys in our class, and two got killed."

During World War II, the students at the school took one-hour turns in a cubicle on the roof, reporting all aircraft to authorities. Some of the girls volunteered at the courthouse with the ration board. Many of the boys joined the Commandos, a school group formed to prepare them for the Army.

The big rivalry was with Surrattsville High in Clinton, whose students were dubbed the Sewer Rats by the Marlboro students.

The senior prom was in the school auditorium. After dances, they would go to Wayson's restaurant, in nearby Anne Arundel County.

In the '40s, Upper Marlboro was more than the county seat. It was a thriving tobacco town, with a population probably not much smaller than the 796 who today reside within its small town limits, but with only country outside it. There were no shopping centers, no subdivisions.

Main Street had three grocery stores, a pharmacy, a movie theater (Sidney Lust's Marlboro Theatre--children, 20 cents, with blacks required to enter through the back door and sit in the balcony), three banks, a bowling alley and, of course, the courthouse. The school playing fields were where the County Administration Building is today.

The town had three schools then--Marlboro Elementary and High School, for whites, St. Mary's Catholic school and Douglass, for blacks. Now there are none.

Route 4 did not exist. All traffic flowed through town, along Main Street, and it was especially heavy during the summer, when beachgoers went to the Western Shore resorts, and during the 10 days in September when the horses ran at the Marlboro Racetrack--now the Prince George's Equestrian Center and Show Place Arena.

It was a society not entirely unlike today's, separated by race and class, but in ways far less subtle than now.

At Marlboro High in 1928, students put on a minstrel show. "Sixty or more boys and girls took the parts of negroes," the yearbook noted. "They certainly were great."

Jane Eagen, 1946 class president and a former president of the Prince George's County Historical Society, recalled a time when her young brother and his best friend, who was black, had to attend separate schools. She said her brother took his friend to their basement and painted him white so they could stay together.

In the white community, there were also divisions. The children of the gentry attended public elementary school, then often went off to boarding schools and college.

Recalled Hoffman, "Sasscer, Wyvill--that was highbrow. They were friends in school, but then they'd go different paths. It was definitely a class thing. Most of the girls in the upper class went to Hood College. . . . The first elder hostel I went to was Hood College. I wanted to see how the other half lived."

Marlboro's high school students moved in 1948 to the new Frederick Sasscer High at the edge of town. It was named after the county's first school superintendent and now houses the county Board of Education. The old school continued with primary grades and then administration until 1974, when the county took it over.

The idea for the boulder and plaque was hatched at the 50th-anniversary reunion of the Class of 1946. "I got nowhere real fast," said Dodd, who sought to obtain permits he ultimately learned he did not need.

"We found a rock we liked very much," he said. "It's quartz white with pink in it." The boulder was donated, but the alumni had to pay to have it hauled to the site.

Five former teachers came to the dedication, including Ellen Bowling Smith, 94, Adelaide Traband Binger, 96, and Marie Parrish, 87. Smith and Binger, who taught in the primary grades, were themselves Marlboro High graduates.

Parrish came from Nebraska to teach. "I had difficulty understanding them," she said of her new charges. "They had a southern drawl. When I first came here, I thought the Civil War was going on here yet. You had to be careful how you talked."

That has changed, of course. But some things haven't. Many of the graduates of Marlboro High still live in and around Upper Marlboro, some even in the homes and on the farms where they grew up. Geraldine Beall Cator, Class of 1943, lives on Ritchie-Marlboro Road, on a part of her father's farm. The Chesapeake Beach Railway ran right through the farm, until it closed for good in 1935, and as a child, she took the train to Marlboro Elementary.

"Everyone is amazed to think I'm still here," she said. "It's been a very good, enriching life. We all have deep roots here, that's for sure. We've never wanted to go any further."

CAPTION: Above, former teacher Adelaide Traband Binger, left, greets Nancy Coffren, whose husband, Buddy, was Binger's student. At right are former teachers Marie Parrish, left, and Ellen Smith.

CAPTION: Helen Hall Ford, Class of 1945, left, hugs Mary Hobbs Tayman, who graduated a year later, after the dedication ceremony. With the women is Marvin Tayman, Mary Tayman's husband.

CAPTION: This plaque marks the spot where Marlboro's white children were educated for 150 years--until high school students moved to the new Frederick Sasscer High School at the edge of town in 1948.

CAPTION: Betty Ann Thorn Pumphrey wears a jacket with the old Marlboro High logo. Seventy-five graduates attended the event Saturday.