Kevin Pack said he liked the Air and Space Museum best. His classmate, Conrad Meub, said he liked the swimming party.

The two youngsters and 13 other sixth-grade students from the Bingham School in rural Cornwall, Vt., spent four days recently visiting Washington as part of a cultural exchange experiment in which students from rural Vermont and urban Washington learned about their differences and many similarities.

The two groups of children met for the first time in February, when students from the Fort Lincoln Community School in Northeast and their teachers visited Bingham School in the first phase of the student exchange program. They had not seen each other since, although they had been exchanging letters for several months. Last week, it was the Vermont students' turn to stay with their pen pals and their families and visit the nation's capital.

Richard Isenberg, principal and a teacher at the Bingham School and a former Washington teacher, conceived the cultural exchange idea. He suggested the experiment to Myrna Riley, fifth-grade teacher at Fort Lincoln Community School, who had helped train him when he was a student teacher. Riley and others helped plan the exchange. Students from the two schools began exchanging letters and studying each other's communities in September.

Teachers and parents made the travel arrangements, holding expenses to a minimum: $49 for round-trip tickets on Amtrak and $15 per child in spending money. There were no housing costs because students stayed in the homes of the pen pals.

"It's been a real cultural exchange and you can't ask for more," said Isenberg, who added that the program was a tremendous success largely because of the parents. "The children spend most of the time with the families--the parents," he said.

Before returning to Vermont, the students visited the Capitol, had lunch on the Mall, toured the city by bus, and made field trips to the monuments, the Smithsonian Institution's museums and Howard University's television studio. Their last day was spent swimming in the Fort Lincoln school's olympic-size swimming pool and relaxing at a cookout on the school grounds.

"After one night with our friend Kevin I can tell that the farm ain't what it used to be," commented Washington resident Carl High, Kevin Pack's parent-host, during the farewell cookout. "They are not farm kids. They know all of the latest rock 'n' roll, the latest swing, the hottest cars . . . ."

High, and his wife Sandra, parents of Lawrence Autry, Kevin's pen pal, said they hope the experiment will produce "lasting friendships."

Kevin's father, Robert Pack, also supports the program. "One of the limitations of living in Vermont is that it's not a racially mixed area. There are few black people in the state," he said, "and we feel it's very important for the children to be exposed to other kids and also have a little more of a sense of city life."

The town of Cornwall, the Vermont children said, has a church, a store, a school, a grange hall, 933 inhabitants, lots of trees and woods. The town's main industry is dairy farming, but there also are apple orchards, hay and alfalfa fields and lots of chickens.

Cornwall student Fred Richmond said he and his family live on 325 acres. His father, who drives a truck, built their house. The family has three big tractors, some wagon mowers and rakes and other machinery. Like most of the other Cornwall children, Fred has regular chores. He mows the lawn, feeds the dog and guinea pig and chops wood. He also helps his cousin work on a farm, where he feeds 175 cows and feeds, grooms, waters down and rides "some horses."

Many of the Washington children also have chores: making their beds in the morning, feeding pets or helping take care of smaller brothers and sisters.

Last winter, when the D.C. students arrived in Cornwall, there were two feet of newly fallen snow on the ground. They spent a day skiing on nearby Bread Loaf Mountain and later visited a local dairy farm and stables.

Anthony White, a Fort Lincoln student, summed up his feelings after bidding goodbye to the Vermonters at Union Station: "Why did they have to go? It's kind of sad. One of my best friends from Vermont is Sean Mayo . . . . We had a whole lot of fun together."

Yvette LaRoche, mother of Jamie Critchley of Cornwall, said in a telephone conversation that the Washington trip was her 11-year-old daughter's "very first time" away from home. The mother added that it was hard for her to "let go" of her daughter.

But, LaRoche concluded, it was a good experience for Jamie, a "picky eater." "She grew up a lot and it was good for her to eat someone else's food for a week."