Asian parents are spending billions of dollars on private tutors for their children.
And the practice is growing despite doubts over its effectiveness, says a study published in Manila yesterday.
"Shadow education" is an expanding business not only in wealthy countries but also in some poorer nations as parents try to give their children the best start in life, the Asian Development Bank said.
Nearly nine out of 10 South Korean elementary pupils have private tutoring, while the figure for primary school children in India's West Bengal is six out of 10.
"Proportions are lower in other countries, but throughout the region the shadow is spreading and intensifying," concluded co-authors professor Mark Bray and assistant professor Chad Lykins of the University of Hong Kong's faculty of education.
The 114-page survey was conducted by the ADB jointly with the HKU center. It called for a review of education systems to make such extra teaching less attractive.
In Hong Kong, where 85 percent of senior secondary students receive tutoring, companies advertise the services of "star" tutors on television, in newspapers and on the back of buses, the study said.
In the mainland, 73.8 per cent of primary students are receiving extra lessons, some in non-academic subjects.
Proportions in lower and upper secondary are 65.6 percent and 53.5 percent.
In Taipei, 72.9 percent of Grade 7 students are receiving tutoring for an average of 6.5 hours a week.
Extra academic work is aimed at helping slow learners and supporting high achievers, and is seen by many Asian parents as a constructive way for adolescents to spend their spare time.
However, it can also reduce time for sport and other activities important for well-rounded development, as well as cause social tensions since richer families are able to pay for better-quality tutoring, the study said.
But tutoring has had mixed results.
"In many countries, individuals can become tutors without training, and the effectiveness of some forms of tutoring is doubtful," the study said.
Hong Kong Professional Teachers' Union president Fung Wai-wah noted that tough competition for a university education is driving the tutoring mania.
However, "Tutor Queen" June Leung, who co-founded Beacon College, said the industry provides more choice for pupils.
"We live in a commercial world which benefits from choices but also selections."
Jao Ming, a father of three, said his Secondary Seven son attends four tutorials a month and he spends HK$480, which he considers worthwhile.