Students in Singapore are among the world's most hard- working at home, clocking the third-longest time spent on homework, a report released this month has found.

The country's 15-year-olds said that they devoted 9.4 hours to homework a week, in the study by the Organisation for Economic Cooperation and Development (OECD).

They came in behind students in Shanghai, who spend 13.8 hours a week on homework, and those in Russia, who take 9.7 hours.

Students in Finland and South Korea spent fewer than three hours - the least among the 65 countries and regions surveyed - on homework each week.

The global average was about five hours' worth of homework each week.

The report was based on results from a questionnaire in 2012 for the OECD's Programme for International Student Assessment (Pisa), a test to measure academic achievement for 15-year-olds.

Around 510,000 students took part in the test. They were asked questions about their school environment, families and attitudes towards subjects and school.

The study found that students who did more homework scored higher in Pisa. For instance, Shanghai and Singapore, where students spent much of their time on homework, came in first and second respectively in the Pisa mathematics test in 2012.

Across the countries and regions surveyed, students who came from socio-economically advantaged backgrounds tended to devote more hours to homework.

A spokesman for the Ministry of Education (MOE) said Singapore's weekly average of 9.4 hours on homework is "fairly reasonable for upper-secondary students, who would be preparing for the national examinations".

She said: "Homework, when used appropriately, can reinforce students' learning, contribute to their progress and cultivate a healthy disposition towards learning."

But in response to parents' concerns about excessive homework in recent years, schools have adopted policies to monitor and coordinate the homework load across subjects and departments.

The MOE spokesman said: "Some teachers may get their students to complete their assignments in class or after school, rather than at home."

Swiss Cottage Secondary School student Nurul Amirah, 15, said her daily routine of homework and revision starts at 9pm and ends around midnight.

"I spend more than 10 hours on homework every week. If exams are coming, I spend at least 15 hours. But I benefit from assignments that make me think more," she said.

She added that teachers and students list homework assignments on their classroom boards, so students do not get assigned too much work at any one time.

Associate Professor Jason Tan, an education policy expert at the National Institute of Education, said: "The 9.4 hours do not seem that overwhelming, when students are taking six to nine subjects in Secondary 3.

"But (the report) also doesn't give any indication of the subjects the time is spent on, or the nature of homework, so it's hard to draw any conclusions from this."

Prof Tan added that although students in South Korea and Japan were ranked low in the number of homework hours in this survey, they were not "learning any less".

"Their students spend long hours after school in cram schools similar to tuition centres, called juku in Japan and hagwon in Korea," he said.

It is difficult to set a "right" amount of homework for everyone, said Prof Tan.

"Every student is different in terms of learning styles and interests, and each may need a different amount of time for practice."

ateng@sph.com.sg