They boast of weekend jaunts to Belgium and summers in London. Their clothes are branded with Calvin Klein and Gloria Vanderbilt labels. They go home to swimming pools and watching Daddy on the evening news.

Meet the jet-setters of the elementary school crowd, the fashion plates of the playground, the sons and daughters of the rich and the famous and the powerful.

"We were supposed to go to Europe on the Queen Elizabeth II this summer," 11-year-old Richard Blackwell said wistfully. He frowned, disappointment etched on his face, and muttered, "But it got sent to the Falklands and now we're just gonna go over on the Concorde."

For a kid who took 15 airplane trips last summer, the Concorde is just another plane ride.

Blackwell attends Franklin Sherman Elementary in McLean, a public school that enrolls youngsters from some of the wealthiest, best-traveled, best-known families in Fairfax County--and the country. Its roster includes the children of millionaires, members of Congress, CIA officers, diplomats and corporate executives--the kind of kids usually found at exclusive private schools.

"A lot of McLean schools are called the private schools of the public school system," said Carolyn B. Boxley, principal of Franklin Sherman for the past eight years.

Although Fairfax County has a substantial number of affluent families, the largest concentration of them lives in the McLean area, county government statistics show. The average family income in McLean was $53,600 in 1981. That is almost three times the national average and substantially more than the countywide average of $41,600.

In many McLean classrooms, designer jeans and Lacoste shirts are the uniform. Pencils and scissors are stored in Nike and Topsider shoeboxes.

Many of the youngsters are sophisticated beyond their ages and have lived and traveled around the globe.

"It doesn't matter what country you study," said Boxley, "you're going to find some child who's been there or has connections there."

Take Nanette Kane's sixth-grade class at Great Falls Elementary. Twelve of her 29 students have been abroad at least once.

There's Reid Thompson, who's gone fishing with his father in Australia three times--and is going back this summer. After that they're going hunting for water buffalo, although Reid doesn't know where yet.

"You're going all the way to Australia just to go fishin'?" one student asked increduously.

"It's not just fishing," said Reid, whose father is retired. "They're big fish, and besides, my dad's a sports fisherman."

And there's the Great Falls Elementary family that went to Belgium for the weekend. And the girl from Franklin Sherman Elementary who took a quick weekend trip to Hawaii.

"Hawaii? For the weekend?" marveled teacher Bill Pennewell at his student's report. She matter-of-factly explained, "My father's vice president of an airline."

"The standard joke here among the teachers is 'I'm going to Annandale for the weekend,' " said Principal Boxley. That fits Pennewell. Thirteen of the 28 pupils in his sixth-grade class say they've been to a foreign country; 12 of them say they are taking trips abroad this summer. Pennewell isn't in either category.

When the youngsters run out of tales from their exotic adventures, they bring a few signs of their home lives into the classrooms.

Show-and-Tell often tells a lot:

The second grader who brought in his father's wallet--stuffed with at least $2,000 in cash, travelers' checks and francs left from a recent trip to France. The boy was a hit with his friends but dad was frantic, the principal reports.

The sixth grader who borrowed her mother's $7,000 diamond ring to hold her scarf in place around her neck. Mom called the principal as soon as she discovered the missing jewelry. "We went crazy figuring out where to hide it until the mother arrived," Boxley recalled with a chuckle.

Both schools also have a large contingent of "embassy children." For instance, youngsters from 38 countries attend Franklin Sherman. The word "office" is repeated in six languages on a sign near the front of the school.

The diplomatic children often have problems unique to most American schools, public or private. One fourth grader from a wealthy South American family has been traveling around the world by himself since he was 7, but is not allowed to shampoo his hair without the help of servants.

"We had to try to make the mother understand that school is the real world," said Boxley.

Not all of the students are children of the monied and influential. Franklin Sherman, for instance, has a small group of children from families who survive primarily on welfare aid, according to Boxley. And there also are children from several families who have lived in the area for three generations, watching it grow from rural hamlet to chic suburbia.

Still, teachers and principals at both schools say they don't detect much jealousy among students. "The kids are basically sensitive," Boxley says.

But despite what the teachers and principals say, the kids say there are some problems.

Listen to Great Falls sixth grader Shelley Stansbury:

"Sometimes you tell people about your trips and they get jealous," said Shelley, who's been to Canada, Mexico, Germany and Switzerland and whose grandparents take her on a train trip every year as a Christmas gift.

One youngster, distraught that a classmate had been to Florida and she hadn't, demanded that her parents take her to the sunshine state, according to Shelley. She got the trip.

There are few snobs at either school, teachers say, but the students do tend to be isolated from the larger problems of society.

For instance, teachers say many of the youngsters have little concept of poverty or the problems of underprivileged people.

Roberta Sherman, an instructional aide at Great Falls, never considered herself underprivileged. She said her students stamped that label on her when they discovered she didn't own a color television.

"For many of these students, school is not the real world," said Boxley. "At home they have swimming pools and tennis courts and model airplanes that cost thousands of dollars--they see a lot of things at school as mundane tasks."

The students at both schools, teachers say, are among the brighest in the county. Their scores on standardized achievement tests are some of the highest in the school system.

"There is a lot of competition among the children academically," said Great Falls instruction aide Sherman. "They see it at home--at least one parent if not both are college educated."

The sophistication, the travel experiences and the home advantages spill over into the academic side of school life.

"You study a place where they've been," said Katherine Steiert, principal at Great Falls. "It's something familiar, they relate, they perk up, there's a light in their eyes."

And that often pushes their teachers to do a little extra homework. "You feel like you're growing all the time," said Steiert. "If you didn't the children would be on top."