SEOUL -- They are the children and grandchildren of Koreans, high school students in Canada and the United States sent back to experience their heritage. For 10 days in a government-run school, they have been immersed in Korean history, Korean culture and, above all, Korean morality, manners and respect for elders.

Now, as they sit on the schoolhouse stoop awaiting the dinner bell, they spot a stranger walking up the driveway.

"Oh, my God, are you an American?" one girl exclaims. "Welcome to prison camp."

"They lock us in here at night," says another.

"They lock us on the fourth floor to keep us apart from the boys," says a third.

So West meets East in a two-week summer program for 2,000 teen-agers staged each year by the National Institute for Overseas Koreans. For South Korea's government, which considers itself the only legitimate authority on this divided peninsula, the sessions provide one means of staying in touch with some of the 5 million Koreans who live outside South Korea.

For Korean-born parents in strange lands, summer school may help narrow the inevitable gap between immigrant and offspring. With luck, it also may counter the puzzlingly loose morality of their adopted cultures.

And, despite the duress of curfews and Korean-style discipline, many young people here said the two weeks have helped them grapple with troubling issues of identity and fitting in.

"I've learned to appreciate my parents more," said Nina Kim. "I've learned to understand why they are the way they are and why they push the way they do."

"I expected to have more fun," said Jennifer Bae, 18, of Ventura, Calif. "I was in for a shock when I came here. . . . But I've learned a lot." About 1 million Koreans and Korean-born expatriates live in the United States and Canada, most having arrived since the Korean War of 1950-53. (Another 2 million live in Manchuria, 1 million in the Soviet Union, 700,000 in Japan and others in many countries.) Many Koreans living in the United States have excelled in school and prospered in business, working as hard as their relatives in this startlingly industrious country.

Most of them also maintain strong ties to the "motherland." Dr. H. S. Song, an Ontario scientist, said his 18-year-old daughter asked to be sent this summer. "She wanted to know her identity, which they couldn't give her in Canada," he said. "She thought she was Canadian, but she's not . . . If you don't know what you are, you should be ashamed."

South Korea has no desire to woo anyone back permanently, according to Moe Young-kee, president of the Overseas Koreans institute.

"We have too many people already," Moe said. South Korea, with about 42 million people, is the world's fourth most densely populated nation. "Our government policy is that they should be good Americans, but with their Korean heritage, too," Moe said.

To that end, his institute subsidizes the summer camps (students pay air fare plus $300) and supports 600 Korean schools around the world, including one in Rockville, that mostly offer classes on Saturdays. It also selects 40 volunteer teachers from those schools for a two-week course in Seoul each year.

Suzie Chae, whose Korean name is Chae Hyang-su, was one of the teachers selected this year. A 24-year-old psychology student and secretary in Los Angeles, she left South Korea 10 years ago.

"When I went to high school, I didn't think that much about being Korean, I just wanted to fit in," she said in an interview as the training session ended last weekend. "But when I went to college, and started to look for my identity, I said, hey, wait a minute. Even though I could speak English and had a lot of good friends, there was still a gap between white and Korean."

About two weeks ago, she returned for the first time. Sitting next to her as the jet touched down were a mother softly crying and a daughter who seemed unmoved. The mother could express herself well only in Korean, and the daughter only in English, so the mother asked Chae to explain.

"I said, 'You're in your motherland, don't you feel anything at all?' " Chae said. "And she said, 'I left when I was 3, it's too long ago.' That's one of the saddest things that could happen to a mother and daughter, not to be able to share the emotions of a once-in-a-lifetime kind of experience."

Trying to expand the common ground, summer school sessions feature tours, home stays and two-hour lectures, mostly in Korean, emphasizing Confucian respect for elders and the importance of Korean tradition.

Not surprisingly, there are some glitches as the Valley girls, cheerleaders and wise guys of America try to adapt.

One unruly high school girl, for example, rubbed her hand insolently over a bald teacher's head, something so unthinkable here that no one could suggest what the punishment should be.

But most said they appreciated the cultural difference. "The biggest difference here is manners," said Kathy Kim, 18.

"In America, I can say, 'Hi, Dad,' or something," said Frank Lee, a cheerful 17-year-old from Palos Verdes, Calif. "Here you have to bow, and Dad eats first."

Many students resented what they felt was condescension from Koreans their age. But the Americans also respected how hard their counterparts study, putting in 15 hours or more each day so they will score well on the university entrance exam. They were shocked to find no dating, no movie-going, seemingly no recreation at all.

"At home we have nerds and brains and jocks," Kathy Kim said. "Here, they're all brains."

But most of the students agreed that high schoolers here also miss out by studying so single-mindedly. "I don't think the Korean system would work for us," said Jennifer Bae, "and I don't think our system would work for them."

Still, most of the students seemed set to return home with a stronger sense of their Koreanness. All students interviewed said they expect to marry a Korean.

"If you're from France or England, after a year or two you can be an American," said Moe. "But if you're Korean, because you're a different color, people will always ask, 'Where are you from?' So you should know where you are from."