Perched high on a hill above the historic Swiss city of St Gallen, set in 25 acres of private parkland, sits one of the most expensive boarding schools in Europe. Costing up to £100,000 for an academic year, the Institut auf dem Rosenberg is more than twice as expensive as Eton college and educates the offspring of some of the wealthiest people in the world. Most of whom, it turns out, will be taught by teachers who trained in the cash-strapped classrooms of UK state schools.

Those teachers who find themselves in Rosenberg’s five-star setting are a small subset of the thousands leaving their students in Oldham and Lewisham, Liverpool and Leicester, and heading for Switzerland, China, Canada, Dubai, Australia, Thailand, Mexico, Nepal and numerous other international education destinations.

When the Guardian visits, the quaint art nouveau villas that form the school campus are shrouded in a bleak mountain mist – making it look more A Series of Unfortunate Events than The Sound of Music. The 230 pupils of more than 40 different nationalities are just back after their half-term break – the younger children are cute and chatty, while the older pupils sidle by with barely a glance.

The Rosenberg offer could not be further removed from your average state school in the UK. Certainly it makes uncomfortable viewing for an education correspondent more familiar with our overstretched comprehensives and academies. While schools in England and Wales have been forced to cut jobs and close early to save money, here pupils are invited to bring their own horses, and meals are served in a high-end restaurant catering for every dietary requirement.

The benefits include small classes, capacity to save, private healthcare, free flights home and no Ofsted

For sports and recreation there is skiing every weekend in the winter, golf training by pros, a health and fitness club, and tennis courts. While teachers in England deliver lessons to 30-plus pupils in each class, the average class-size in Rosenberg is just eight. In England, headteachers are asking parents to donate toilet rolls and glue pens; here the children’s bathrooms are marble-lined and each new younger student is given a Steiff teddy bear to share their pillow. The school is discreet about alumni – apart from the Mexican Nobel laureate Mario J Molina, after whom the school’s science centre is named – but it is happy for you to know it includes European royalty and Silicon Valley entrepreneurs.

Among Rosenberg’s plum teaching recruits is Alex McCarron, from the Wirral. As a physics teacher, he is educational gold dust. According to the National Foundation for Educational Research’s 2019 report into the teacher labour market, recruitment to teacher training in physics is more than 50% below the numbers required to maintain supply. The son of a physics teacher, McCarron trained in a mixed comprehensive and an all-boys grammar and loved every minute of it, but says Rosenberg offered him the opportunity to teach his subject at A-level, which would not have been open to him as a newly qualified teacher in England, so he jumped at the chance.

‘A growing number of British independent schools are opening branches overseas.’ Repton in Dubai.

Besides, here there’s less time spent managing behaviour and more time doing what teachers love – teaching their subject. At home, he says, his work was results- and Ofsted-driven. Here he feels he can be more creative, more independent. “In the UK you are constantly having to report to certain people about certain things. Here you are trusted to do what you think is best for the student.”

Eilish McGrath is head of social studies at Rosenberg and echoes McCarron’s sentiments. She began her teaching career at Hathershaw college in Oldham, a comprehensive with a large number of disadvantaged pupils, followed by a sixth-form college in Macclesfield. She enjoyed the work, but having spent much of her childhood in the Middle East and Asia, she moved to Dubai, where she taught at Repton school, one of a growing number of British independent schools that are opening international branches overseas.

“For me, the weather was quite a big thing,” says McGrath. After seven years she left the United Arab Emirates and moved to her current post in Switzerland. “We are very fortunate,” she says. “If I have an idea I can really make it happen.” She likes the outdoor life available to her in Switzerland, and the class sizes are small. “It provides you with the opportunity to focus on quality of teaching rather than crowd management.”

Rosenberg may not be exactly typical of the overseas schools that UK teachers are flocking to, but it is attracting them for the same reasons. A call-out to Guardian readers for their experiences has drawn more than 300 responses – many heartfelt – from teachers who reluctantly left their jobs in the state sector in the UK to teach abroad, usually in well-funded private institutions. Often exhausted by their experiences in the UK, they complain of excessive workload, stress, a lack of work-life balance, funding cuts, a dread of Ofsted, an obsession with paperwork, accountability measures, poor behaviour, children bringing weapons to school, high staff turnover … the list goes on.

The diversity of destinations is remarkable. Teachers have contacted us from Vietnam, New Zealand, Hong Kong, Azerbaijan, Qatar, Spain, Italy, Slovakia, Colombia, Sweden and Germany. They wrote from France, Bali, Singapore, Seychelles, Tanzania, the US, South Korea, Brunei, Japan, Hungary, Belgium, Oman, Jordan, the Czech Republic, Bahrain, Ghana, Ireland, Russia, Zambia, Luxembourg, Cyprus, India, Latvia, Ecuador, the Philippines, the Netherlands, Israel, Uganda, Kuwait, Borneo, Peru, Austria, Kazakhstan and Hungary. Not forgetting Ascension Island, Egypt, Myanmar, Norway, Saudi Arabia and Moldova.

The benefits of working abroad, they say, don’t just include sunshine, free accommodation and tax-free earnings, but small classes, more resources, better work-life balance, freedom to travel, capacity to save, private healthcare, free flights home and no Ofsted. Their strength of feeling is eye-opening. “I would burn in hell before returning to teach in an English school,” says one teacher who moved to the Netherlands. “Teaching in the UK is exhausting,” says a secondary school art and design teacher who moved to an international school in Thailand.

Though few of the teachers who contact us are motivated by money, one 33-year-old left her primary school in Tower Hamlets, east London, for an international school in Yangon in Myanmar because she couldn’t make enough money to survive in London. Now she earns £5,000 more, plus a yearly bonus, in a package topped off with free accommodation, flights and medical insurance. “Working conditions are better, with sizes that are half of a UK class. It would be insane for me to return to the UK.”

‘The pupils are delightful, classes are small, resources are plentiful, workload is reasonable, staff work well together.’ Two Boats school, Ascension Island.

Janet Birch, a science teacher, left the UK for Two Boats, the government school on Ascension Island, a British Overseas Territory in the south Atlantic. In her north London secondary, she felt that the workload was excessive, pupils were poorly behaved, resources were tight and the job was stressful. “I could be earning more in England but I would not be able to save as much,” she says. She described her new situation: “The pupils are delightful, the classes are small, resources are plentiful, workload is reasonable, staff work well together.” Island life suits her – she dives, walks and is a projectionist for the local cinema.

The alarm bells have been ringing for some time about the exodus from our classrooms. One poll by the National Education Union (NEU) this year found that one in five teachers (18%) expects to quit in less than two years, and two in five want to quit in the next five – most blame “out of control” workload pressures and excessive accountability.

“We know that teachers have a strong social mission and they want to make the world a better place, and work with disadvantaged children,” says Mary Bousted, joint general secretary of the NEU. “But the reality is we are making teaching just too hard to do.”

I remember spending weekends in the UK sat inside planning, marking, assessing, worrying … Now I actually have a life

Louise Sturt, an English teacher with 25 years experience in the state sector in England, would agree. She finally quit her comprehensive near Bristol after years of funding cuts, restructuring and deteriorating behaviour. Staff numbers had been reduced dramatically, she says. She now works at the private Dubai English Speaking college. “We’ve got a nice place to live. We’ve got sunny days every day. It feels like an adventure.” After so many years in state education, she feels sad she has finally “gone over to the other side. I would go back to it. There are not that many people I speak to who would.”

On the other side of the planet, Katy Bull is thriving in her role as head of kindergarten in a small international school in Tequisquiapan, a popular tourist town in central Mexico. “I remember spending weekends in the UK sat inside planning, marking, assessing, worrying … Now I actually have a life. I would still say I work extremely hard, but extremely hard on the things that count. I feel intrinsically motivated to be an outstanding teacher, and not because Ofsted inspectors are pressuring me.”

Modern foreign language teacher Mary McCormack, who quit her job at a school in Wolverhampton for Canada, has similar memories of weekends and “the piles of books that needed to be corrected every three weeks – robbing me of my Sundays”. And in Quebec? “Little to no lesson observations. Complete trust as a professional. I am paid more, but the high taxes mean that my take-home is slightly less than what it would be in the UK. This being said, I would never consider coming back to a British classroom.”

In the run-up to a general election in which education is likely to be a key battleground, all parties have pledged more money for schools. The Tories have promised increased starting salaries for teachers of £30,000, while Labour pledged an end to high-stakes school inspections, but whether any of it is enough to stem the exodus of teachers remains to be seen.

Prof John Howson, an authority on the labour market for teachers, says it is classroom teachers with between five and seven years’ experience that are being lost in greater numbers than ever – the very people who should be moving into middle leadership positions. And while once upon a time they might have gone abroad to work in the international sector temporarily, Howson fears these days they may prefer what they find overseas and not return.

What’s more, a significant increase in the number of secondary school pupils is projected over the next few years. This means we will need more teachers, not fewer, just at the time the international schools market is booming and will be trying to lure British teachers in ever greater numbers to fill its classrooms overseas. According to the Council of British International Schools, the sector will require up to 230,000 more teachers to meet staffing needs over the next 10 years. “I fear that we may have to go looking elsewhere around the world for teachers to come and work here,” says Howson.

In Switzerland, McGrath contemplates a different future, away from the exclusive surroundings of the Institut auf dem Rosenberg, back to her classroom in Oldham. “Would I go back and teach in the UK?” She sits back and reflects. “When I worked in Oldham, I really liked the challenges of the students I was working with. Now working here, I would find it very hard to go back.”