Authorities throughout South Korea have taken extraordinary measures to minimise possible distractions, including rescheduling 134 flights.
South Korea dialled down the volume on Thursday, as more than half a million students sat a crucial national university entrance exams.
The college entrance test is the culmination of South Korea's highly demanding school system.
In an ultra-competitive society the rite of passage plays a large part in defining students' adult lives, holding the key to top universities, elevated social status, good jobs, and even marriage prospects.
South Korean President Moon Jae-in posted good luck messages to the students on his Facebook page and Twitter.
The intense effort they had put in over years of study was coming to fruition, he said. "Believe in it and you will be able to show your full competence."
According to the education ministry nearly 595,000 students were sitting the gruelling exam this year, known as "suneung" and stretching over nine hours.
Junior students crowded schools from early morning ahead of the test, chanting and waving colourful banners with messages urging: "Don't mess up!"
At Ewha Girls' Foreign Language High School in central Seoul, Jung Ho-yun said: "Their lives depend on this exam, so it’s very important."
The test takers briskly arrived one by one, looking anxious and flustered.
"I can't believe this is actually happening," said Choi Eun-hee. "I just really hope I don't make any mistakes."
Wiping away tears, parents gave their children long hugs, before some went to temples and churches to pray for their sons and daughters' success.
Extraordinary measures are taken nationwide to remove anything that could disturb the test-takers.
Public offices, major businesses and the stock market opened an hour later than usual to help ease traffic and ensure students arrived on time for the exam, which began nationwide at 8:40 am.
Any students stuck in traffic could get police cars and motorbikes to rush them to the exam centres.
All takeoffs and landings at South Korean airports are suspended for 25 minutes to coincide with an English listening test, and all airborne planes must maintain an altitude higher than 3,000 metres (10,000 feet).
The Transport Ministry said 134 flights had to be rescheduled because of the exam.
Electronic devices are strictly forbidden and students cannot leave school premises until the test ends to reduce the chances of cheating.
But they were allowed to wear masks during the exam this year, the education ministry said, with fine dust pollution levels persisting at "bad" on the peninsula.