SEOUL, South Korea — It is 10:30 p.m. and students at the elite Daewon prep school here are cramming in a study hall that ends a 15-hour school day. A window is propped open so the evening chill can keep them awake. One teenager studies standing upright at his desk to keep from dozing.

Kim Hyun-kyung, who has accumulated nearly perfect scores on her SATs, is multitasking to prepare for physics, chemistry and history exams.

“I can’t let myself waste even a second,” said Kim, who dreams of attending Harvard, Yale or another brand-name American college. And she has a good shot.

This spring, as in previous years, all but a few of the 133 graduates from Daewon Foreign Language High School who applied to selective American universities won admission.

It is a success rate that American parents may well envy, especially now, as many students are swallowing rejection from favorite universities at the close of an insanely selective college application season.

‘Struck a nerve’

“Going to U.S. universities has become like a huge fad in Korean society, and the Ivy League names — Harvard, Yale, Princeton — have really struck a nerve,” said Victoria Kim, who attended Daewon and graduated from Harvard last June.

Daewon has one major Korean rival, the Minjok Leadership Academy, three hours’ drive east of Seoul, which also has a spectacular record of admission to Ivy League colleges.

How do they do it? Their formula is relatively simple. They take South Korea’s top-scoring middle school students, put those who aspire to an American university in English-language classes, taught by Korean and highly paid American and other foreign teachers, emphasize composition and other skills key to success on the SATs and college admissions essays, and — especially this — urge them on to unceasing study.

Letting up a bit

Both schools appear to be rethinking their grueling regimen, at least a bit. Minjok, a boarding school, has turned off dormitory surveillance cameras previously used to ensure that students do not doze in late-night study sessions. Daewon is ending its school day earlier for freshmen. Its founder, Lee Won-hee, worried in an interview that while Daewon was turning out high-scoring students, it might be falling short in educating them as responsible citizens.

“American schools may do a better job at that,” Lee said.

Still, the schools are highly rigorous. Both supplement South Korea’s required, lecture-based national curriculum with Western-style discussion classes. Their academic year is more than a month longer than at American high schools. Daewon, which costs about $5,000 to attend, requires two foreign languages besides English. Minjok, where tuition, board and other expenses top $15,000, offers Advanced Placement courses and research projects.

And, oh yes. Both schools suppress teenage romance as a waste of time.

“What are you doing holding hands?” a Daewon administrator scolded one adolescent couple recently, according to his aides. “You should be studying!”

South Korea is not the only country sending more students to the United States, but it appears to be a special case. Some 103,000 Korean students study at American schools of all levels, more than from any other country, according to American government statistics. In higher education, only India and China, with populations more than 20 times as large, send more students than South Korea.

‘National obsession’

“Preparing to get to the best American universities has become something of a national obsession in Korea,” said Alexander Vershbow, the American ambassador to South Korea.

Korean applications to Harvard alone have tripled, to 213 this spring, up from 66 in 2003, said William Fitzsimmons, Harvard’s dean of admissions. Harvard has 37 Korean undergraduates, more than from any foreign country except Canada and Britain. Harvard, Yale and Princeton have a total of 103 Korean undergraduates; 34 graduated from Daewon or Minjok.

Kim Hyun-kyung, 17, scored perfect 800s on the SATs verbal and math tests, and 790 in writing. She is scheduled to take nine AP tests next month, in calculus, physics, chemistry, European history and five other subjects. One challenge: She has taken none of these courses. Instead, she is teaching herself in between classes at Daewon, buying and devouring textbooks.

So she is busy. She rises at 6 a.m. and heads for her school bus at 6:50. Arriving at Daewon, she grabs a broom to help classmates clean her classroom. Between 8 and noon, she hears Korean instructors teach supply and demand in economics, Korean soils in geography and classical poets in Korean literature.

At lunch she joins other raucous students, all, like her, wearing blue blazers, in a chowline serving beans and rice, fried dumpling and pickled turnip, which she eats with girlfriends. Boys, who sit elsewhere, wolf their food and race to a dirt lot for a 10-minute pickup soccer game before afternoon classes.

Back to class

Kim Hyun-kyung joins other girls at a hallway sink to brush her teeth before reporting to French literature, French culture and English grammar classes, taught by Korean instructors. At 3:20, her English language classes begin. This day, they include English literature, taught by Mani Tadayon, a polyglot graduate of the University of California at Berkeley, who was born in Iran, and government and politics, taught by a former Wall Street lawyer, Hugh Quigley.

Evening study hall begins at 7:45. She piles up textbooks on an adjoining desk, where they glare at her like a to-do list. Classmates sling backpacks over seats, prop a window open and start cramming. Three hours later, the floor is littered with empty juice cartons and water bottles. One girl has nodded out, head on desk. At 10:50 a tone sounds, and Kim heads for a bus that will wend its way through Seoul to her home south of the Han River.

“I feel proud that I’ve endured another day,” she said.