Hong Kong's schools are often noted for their low levels of violent, anti-social and disruptive behaviour - the bugbears of secondary and even primary education in many industrialised, Western countries.
But many of the territory's students face other behavioural issues, which can have just as great an impact on their own educational progress and may even affect the pace of the whole class.
Elvis Tse Yau-tat, a teacher at Chan's Creative School in North Point, says the main problems are inattentiveness, refusing to engage in lessons and lack of sleep, often due to spending too much time online or playing computer games.
'Many live in their own world,' he says. 'Most Hong Kong kids do indoor activities rather than go outdoors playing sport. The result is, it's hard to get their attention.'
Wong Po-yee, another teacher at the same school, says there is a widespread lack of self-confidence among primary pupils, which is manifested in different ways but seems to start at home.
'Mostly it's their lack of confidence, and this goes across all children,' she says. 'Some don't even believe they can finish their schoolwork. They have no way to express their emotional problems at home. Some show this by being withdrawn or overactive.'