'It's growing in Europe and if they are not careful these countries will have the same problem as in Hong Kong, Korea and everywhere else,' says Bray, who was appointed the Unesco chair professor of comparative education and director of the Comparative Education Research Centre (CERC) at the University of Hong Kong in May.

Announcing his appointment, the university said Bray's field of expertise was 'the study of private supplementary tutoring, a sector that allows wealthy families to secure a good education for their children while those from low-income families fall behind'.

Led by South Korea, where nearly 90 per cent of its elementary students receive some sort of shadow education, Asia is home to the tutoring business. A survey by Bray last year found an astonishing 72 per cent of sixth-formers in Hong Kong get tutoring help. As is the case elsewhere, the service providers range from university or even secondary students finding ways to augment their income to large tutorial-centre chains listed on the local stock market.

'Shadow education is much less about remedial help for students to keep up with their peers and much more about competition and creation of differentials. It may also contribute to inefficiencies in education systems, and even to elements of corruption,' Bray wrote in his latest booklet on Asia, published in April by CERC.

The booklet details the impact of tutoring on students' personal growth, social equality and school systems.

'We proudly say that our education system is free; the front door says it is free but the back door says give me money,' Bray says. 'The tutoring can make teaching in school more difficult because it increases diversity within the classroom. Some kids respect their tutors more than their teacher; it can create inefficiency in the school system. It's a shadow that affects the body that it is imitating.'

A long-time Hong Kong resident before leaving for Paris, he maintains that despite all the stress brought on by the reform of the school sector, the local system is not without quality. Local students came out top in international assessments such as the OECD Programme for International Student Assessment. Bray blames the tutoring culture on the stiff competition for university places.

Until the mid-1990s, Hong Kong had only two universities offering places to an elite 2 per cent of school leavers. The university admission rate is now 18 per cent after the elevation of a number of former polytechnics to university status.

'As you increase university places, you put university within reach of more people who are aspiring to go to university,' Bray says. 'Then you stratify universities, which university and which course students are getting. All of this has opened up things up and made things more competitive rather than less. It is coupled with an anxiety syndrome, which the tutorial schools are very good at leveraging. They are experts in cranking up anxiety.'

Globalisation further intensifies competition, he adds, comparing tutoring to the cosmetics industry, which is self-generating by increasing people's level of personal consciousness.

As found by a Bray survey, peer influence exacerbated the trend. When asked why they attended classes delivered via taped lectures instead of live teachers, some respondents to his survey said it was because they were slightly cheaper or their friends were there.

'They say they also go because of the peer grouping, a bit like going to church, going with the community at a designated time,' Bray says.

Tutorial schools further grab teenagers' attention by promoting stylish, well-groomed tutors and running in newspaper ads pictures and names of clients who have got top grades in public exams - information Bray warns can't be verified.

'Some tutoring schools are very good at attracting students who get As,' he says. 'It is hard to unpack what is the factor, to know precisely who is working and who is not in explaining which students get As.

'The empirical evidence does not indicate a consistent, positive correlation between time spent on tutoring and increased academic achievement. In some settings inefficiencies are expanded further when students pay more attention to tutors their parents are paying for rather than to school teachers, who seem to be free of charge and who may be taken for granted.'

In a section on non-formal education, the Education Bureau website provides tips on what to look out for in tutoring, such as making sure a school is registered with the bureau, meaning primarily they deliver courses in approved classrooms and comply with fire safety regulations. But more may need to be offered.

Paul Arkwright, chairman of the Hong Kong Federation of Private Educators, which represents centres with just over 50 per cent market share, said he often came across advertisements for schools that were not licensed with the bureau.

Some tutorial centres evade the requirement to register if offering classes to eight or more persons at a time by running them in the evening or at weekends, when Education Bureau inspectors are off duty.

Rather than seeking a policing role for a sector with cut-throat competition, Arkwright's organisation instead advocates a voluntary code of ethics for members. It issues a quality Q-Mark to members abiding by the code, which centres on basic standards like honesty and compliance with local laws.

'As we get more members we will have more manpower to help us go out and at least self-regulate,' he says.

'We regularly meet to talk about what is going on in the industry, the challenges we are facing. Meetings are a very good ear for us.'

To Arkwright, a larger problem lies in parents' attitudes.

'In Hong Kong what I see all too often is this duty of parenting being outsourced to helpers on a day-to-day basis and help with homework being outsourced to tutorial centres,' he says. 'Parents don't understand that after going to the tutorial lessons, it is also important for them to follow up, at least check through it, and talk to the children about it.'

He adds: 'One thing that is sadly wrong here is the massive overemphasis on preparing students for exams and model answers, not preparing them for life.'

Bray acknowledges the difficulties in enforcing regulations. For example, star tutors have found ways to circumvent the stipulation of maximum class size of 45 students by constructing lecture theatres with glass partitions. Tutors teach in one segment, leaving students in other segments watching video screens.

But he still favours more regulations or self-regulation for greater consumer awareness and protection. As cited in his study, South Korea has resorted to measures such as limiting the operating hours of the centres, launching social awareness campaigns and reforming assessment systems.

'Some jurisdictions require tutors to provide evidence of no criminal record, and there can be a case for regulations on advertising, what sort of claims can be made in advertisements, etc.,' says Bray.

His CERC booklet concludes: 'Policy makers may learn from the shadow. They should ask why it exists in the first place, and what can be done in the mainstream to make supplementary tutoring less desirable and necessary.'

$1m

Star tutors have been known to be paid at least this many HK dollars a month for their pulling power