'I study hard to achieve my dream'
2 December 2013 Last updated at 18:23 GMT
The results of the international school tests - known as Pisa tests - have been published by the OECD.
In previous years, South Korea has been one of the highest achievers - but it means long hours of study for the country's pupils.
Between waking up at 6.30am and getting home at 11pm, 16-year-old Hye-Min Park spends most of each day devoted to study.
As well as normal school, she attends a private cramming session or hagwon, followed by more self-study in the evening.
Hye-Min spoke to BBC News about why she is prepared to take on such a punishing schedule.