Singapore's children do not get enough sleep. But it is a necessary trade-off, said some parents.

Given the competitive environment here, it is important their kids spend time on extra classes and enrichment activities, they said.

Contrary to popular perception, school and schoolwork are not the only - or even main - reason why some pupils do not have enough sleep, based on interviews The Sunday Times did with 10 families.

Instead, factors like a hard-striving attitude, lessons outside school and a lack of parental supervision seem to be the biggest culprits.

One parent, who wanted to be known only as Madam Lew, 45, said her 10-year-old daughter who is in Primary 5 participates in activities such as sailing, netball and enrichment classes, as well as ad hoc writing competitions. She sleeps about eight hours a day, and is often tired.

Last month, the NurtureSG committee, which promotes the physical and mental health of children, issued a batch of recommendations. Those aged between six and 13 should have nine to 11 hours of sleep a night, it said. This is in line with similar guidelines by the United States' National Sleep Foundation.

Said Madam Lew: "It's not because of the school's schedule. It's about what she's trying to prove."

Then there's Javier Lim, 11, a Primary 5 pupil at West View Primary who gets about 71/2 hours of sleep due to co-curricular activity (CCA) commitments, maths olympiad classes, and private tuition.He said: "I'm used to it. If I were to call this busy, I wouldn't be able to manage my mid-year, or end-of-year exams."

Most families said their children have about eight hours of sleep every night - below the recommended nine to 11 hours.

Last month, the NurtureSG committee, which promotes the physical and mental health of children, issued a batch of recommendations.

Those aged between six and 13 should get nine to 11 hours of sleep a night, it said. This is in line with similar guidelines by the United States' National Sleep Foundation.

Experts stressed the need to cultivate good sleep habits from young, and pointed out that a lack of sleep has a negative effect on cognition.

On the bright side, some schools have initiatives that promote a better work-life balance for pupils.

Hougang Primary School has since January incorporated CCAs into curriculum time. Pupils no longer stay back after school for CCAs, which could last till 5.30pm before.

It is not known how common this practice is among schools here.

Housewife Wong Fei Wan, 42, whose daughters are in Primary 2 and Primary 5, said they spend an hour in the playground in the afternoon, and sleep for about 91/2 hours.

Still , the demands of homework can take their toll.

Housewife Emmanuelle Tan, who is in her 40s, has a daughter in Primary 5 who attends the Gifted Education Programme at a top primary school - more than an hour away from home by public transport.

Her daughter, who sleeps at 11.30pm and wakes up at 5.30am, often spends about three to four hours on homework daily, including graded project work that is set even during exam periods.

She also has eight hours of tuition a week, full-day chess tournaments on some weekends, and weekly classes with a g randmaster.

"She feels very tired and dozes off a little in class," said Madam Tan.

Some people have suggested that early school hours - starting at about 7.30am - could be a problem.

One parent, Ms Yap, 40, whose children attend Opera Estate Primary, disagreed. "If you start late, you will end late. I don't like the idea of them having a late lunch."

Then there are students who stay up late using social media. One primary school teacher, who wanted to be known only as Madam Ong, 49, said: "Some students look very tired, but that's not due to homework. It's due to gaming, Facebook, Instagram... Some parents don't supervise them because they are so busy."

Others, she said, stay up late to wait for their parents to get home.

Government Parliamentary Committee for Health chairman Chia Shi-Lu said that while many are aware of the importance of adequate sleep, having more people act on this requires a mindset change.

"It's the same as exercise... The question is how to make sure we have the necessary discipline."