Welsh students try South Korea's hagwon night schools
Three Welsh teenagers swapped school life in Pembrokeshire for lessons in South Korea to find out why the country's students perform so well in Pisa tests.
The tests involve 15-year-olds in more than 70 different countries sitting the same exams in maths, science and reading, every three years.
One obvious difference between the education systems is the long hours South Korean pupils put in, with hours of self-study and private night school classes – or hagwons - after lessons end.
The government has now placed a 22:00 curfew on hagwons, but schools stay open until midnight if students want to cram in an extra couple of hours study before bed.
You can see School Swap: Korea Style between Saturday 1 April and Tuesday 4 April at these times on BBC World News.