South Korea as a whole ranks first among O.E.C.D. nations in suicide and is routinely among the leaders in developed nations. Subway stations in Seoul have barriers to prevent people from jumping in front of arriving trains, and eight bridges in the capital have installed closed-circuit suicide-watch cameras.

Suicides of singers, models, beloved actors, athletes, millionaire heiresses and other prominent figures have become almost routine in South Korea. A former president, Roh Moo-hyun, threw himself off a cliff in 2009 after losing face with his countrymen.

But the suicides of the four Kaist undergraduates — three jumped to their deaths and a 19-year-old freshman overdosed on pills — have stunned the nation in a profound and poignant way. (The professor, a biologist who was reportedly being audited for the misuse of research funds, hanged himself on April 10.)

The competition for a place in a leading university begins in middle school for most South Korean students. More than 80 percent of Korean young people go to college, and parents here spend more money per child on extra classes and outside tutoring — including military-style “cram schools” — than any other country in the O.E.C.D.

The pressure builds to a single day in November, when a national college entrance exam is held. Some mothers pray at churches or temples throughout the day as their children take the test, which is given only once a year and lasts nine hours. The South Korean Air Force even adjusts its flight schedule so as not to disturb the test takers.

The ultimate goal for most students is acceptance at one of the so-called SKY schools — Seoul National, Korea or Yonsei universities. In South Korea’s status-conscious society, a degree from a SKY school is nearly a guarantee of a big career and lifelong prosperity. Pedigree is everything.

But Kaist is different. The university pays no regard to the national exam and instead recruits almost all of its students from among the elite seniors at special science-oriented high schools. Kaist admits only about 1,000 freshmen each year. A personal interview, high school grades and recommendations from principals count the most.