In a few weeks' time, 60-year-old teacher, former surveyor and overseas aid worker Robert Booth will travel from the UK to Chitral in the Hindu Kush to be interviewed for the headship of Langlands School to replace 93-year-old Major Geoffrey Langlands, the driving force behind an educational mission that has transformed the life chances of generations of children in this remote tribal region.

Booth was headhunted for the post by David Game, principal and chief executive of the David Game College group in London. Langlands School is a charitable foundation rather than an international school but the selection process is just as rigorous. "The job description is basically someone who can gain the respect of staff and students and ensure that the tradition of Major Langlands is carried on," Game says.

Each year thousands of English-speaking teachers from the UK, US, Canada, Australia, New Zealand and South Africa head for international schools all over the world. They will have been hired at recruitment fairs, signed up by specialist agencies, or they may have responded to advertisements in the press or via websites such as the US site TIE Online, a jobs list of international teaching posts. The demand for staff to teach in English-medium international schools demonstrates the confidence of an education sector that has been growing rapidly, particularly in Asia, where there are currently 3,000 schools employing 134,045 staff. Worldwide, international schools employ about 265,000 teachers, a number that has risen threefold in the last decade.

Based in Sydney, Australia's international teacher agency Teacher Recruitment International specialises in hiring teachers for international schools. "Your teaching certification must be current and you must have qualifications appropriate to your teaching field," advises Robert Lee, director of TRI. He adds. "Interest in teaching roles from Australian, New Zealand, Canadian, US and UK teachers remains strong. There is definitely an expanding market, except for placements of overseas teachers into the US and the UK." According to Lee, the most popular destinations for Australian and New Zealand teachers are Vietnam, China and other parts of Asia.

The Asian tiger economies have led the expansion of international schools as globalisation of business has attracted expatriates and their families to settle in cities such as Beijing, Mumbai and Seoul. The wealth generated by the economic boom is also creating a local middle-class willing to invest in their children's education.

With 420 pupils on roll, Harrow International School Beijing employs 50 English-speaking teachers. "We advertise in the Times Educational Supplement, online and through our own website," says headteacher Matthew Farthing.

The syllabus taught by an international school will determine where it recruits its English-speaking teachers. The American International School in Abu Dhabi not surprisingly recruits mainly Americans. The school adopts Virginia state standards and teaches a modified US syllabus.

Most teachers at AIS are either Americans or Canadians with a few South Africans. The school is part of the Esol Group, a Gulf-based group of international schools, and vacancies are filled at US recruitment fairs.

Although the supply of qualified and experienced staff is enough to meet current demand, rapid expansion in international schools could lead to teacher shortages, warns Andrew Wigford of the recruitment agency Teachers International Consultancy. He says, "We're a long way from teacher shortages but the expansion in international schools means that it is possible schools will soon have to look further afield when it comes to recruitment as well as having to invest money in training their own."

Wigford points to excellent career progression. "Because international teachers tend to be younger and more proactive, opportunities for promotion come up much more often."