What examinations must children take first before going to university in the man

W: At what age do children start school in your country?
M: At five. How about in your country?
W: At six. Do boys and girls go to school together?
M: Yes, they do. And I think it’s a good idea.
W: Do some children go on to university?
M: Yes, they do.
W: What examinations do they take first?
M: "O" levels and "A" levels.
W: Oh, but in our country they take "O" levels and "H" levels. How long do they usually stay at university?
M: Three or four years.