The English education system is broken, says Freya Odell, a state secondary school teacher with 18 years’ experience. This month, she followed in the footsteps of thousands of other talented, fed-up teachers and moved abroad – in her case, to St George’s British International School in Rome.

“It wasn’t a difficult decision. My job in England took over my life. Over the past year, I had stopped laughing and smiling. I had lost all sense of who I am.”

Despite being director of learning, literacy lead and director of English at her previous school, Odell, 38, had to teach 20 out of 30 lessons and mentor three new staff. “I had to get up at 4.30am to get everything done, returning home at 7pm and working for another hour before bed, as well as at weekends.” She offered to take a pay cut to reduce her teaching load, but was refused.

In Italy, she has been allocated the same amount of teaching but none of the responsibilities – and she will teach a class of 16 children, instead of 34. “If St George’s will have me for ever, I will never return to teaching in England,” she says.

As the new school year gets under way, an Education Policy Institute report has highlighted how the government’s failure to recruit enough trainee teachers to stem the flow of experienced staff leaving the profession has led to a “severe shortage” in England’s schools.

It is estimated around 15,000 teachers leave the UK each year to join an international school – and nearly half (47%) are dissatisfied with the British education system, according to a recent survey of 1,600 teachers at British international schools by the Council of British International Schools (Cobis). Around a third (32%) were thinking about leaving the profession altogether before they took on an international job.

Headteacher Binks Neate-Evans moved to a school in Jeddah, Saudi Arabia.

“There’s a toxic mix of factors, created by this government, that is making teachers decide they cannot teach in England in particular any more,” says Mary Bousted, general secretary of the National Education Union. “The low net pay of teachers means many cannot even afford rent. There is systemic overworking, with teachers routinely working 55 hours a week, and a vicious accountability system, which means teachers are not given the time and support to get better at what they do.” It reflects badly on the government, she says, that so many highly qualified teachers are going abroad. “It’s not that they don’t want to teach, it’s that they don’t want to teach in the context we’ve created in this country, and the government is responsible for that. We are haemorrhaging teachers, particularly at secondary school level.”

Teaching timetables in the UK are similar to the OECD average. “But our teachers spend twice as long as other teachers in high-performing OECD countries preparing lessons, assessing and looking at data. It is that, combined with low pay, which is driving teachers away. The very measures the government has taken to police standards are decimating the numbers of teachers in the classroom and lowering educational standards.”

Meanwhile, four in five British international school teachers say they are happy or very happy with their new jobs, according to the Cobis survey. “Other countries exercise much more trust in their teachers,” says Bousted. “They enable their teachers to concentrate on what’s important.”

Over the next 10 years, it is expected that international schools will require up to 230,000 more teachers to meet staffing needs – 145,000 of them will be recruited from the UK, ISC Research predicts. If so, according to Schools Week, international schools could snap up more than half of all the UK’s trainee teachers over the next 10 years to meet their targets.

According to Nick Gibb, the schools minister, more than 14,000 teachers returned to teaching last year, many of whom had been working abroad. “A period teaching in another country has always been an option which adds to a teacher’s experience,” he said.

In Italy, Odell enjoys lower living costs and free lunches, so expects to be better off despite a lower salary. “I feel optimistic that I’ll develop as a teacher here while still maintaining a healthy work-life balance.”

This was partly why Binks Neate-Evans moved to Jeddah, Saudi Arabia, this month as head of prep for a prestigious fee-paying school. In the UK she worked 65 to 70 hours a week as the head of an outstanding infants’ school in Norfolk, where 90% of the children came from the poorest 10% of postcodes in the county.

She says: “We had very limited resources. If you have a child with significant behaviour challenges because of childhood trauma, you need access to a clinical psychologist. For example, there was a child we worked with tirelessly to keep in school, to keep him safe. He absolutely needed specialist support but children’s mental health services said they were taking only life-threatening cases.”

The child was later excluded from junior school. “Despite government spouting off about the importance of early intervention, it wasn’t there. Due to this lack of resources, the needs of very young children at my school were not being met.”

The job left her with high blood pressure and, like her colleagues, she suffered chronic stress and insomnia. “I feel like I’ve done my bit and I was not prepared to compromise my personal health.”

With 23 years’ experience as a teacher, 12 as a head, she found it easy to get a job abroad, choosing Jeddah because the teaching profession seemed highly valued there. Now her earnings are tax-free, her transport to work is paid for, and she has a complimentary two-bedroom flat. “It’s the equivalent of getting a six-figure salary in the UK.” She is not sure she will work in Britain again.

Jenny Anderton (not her real name), 51, who taught at state primary schools in southern England for more than 10 years, says that in the UK she was “more of a social worker than a teacher”. She is now teaching in Seville. “I love teaching, but it was frustrating at my UK school – there was a lot of paperwork and meetings for the sake of meetings,” she says.

The last straw came when a child who had severe emotional issues was excluded. “I had flagged up that he needed help. He was a child in crisis.” Instead of supporting him, the school involved the police when he bit another teacher.

Anderton’s wages are £500 less a year but she is confident she will be better off because of the lower cost of living. “I’m looking forward to being appreciated, rather than having the whip cracked over me all the time, and enjoying my job again, rather than being comatose at the end of every half term. The focus in the UK on attainment, when social services is on the brink, is bonkers and exhausting. I’m not planning to ever go back.”

“Teaching in the UK is a thankless task,” says Victoria Mitchell, 39, who has taught at state primary schools in Nottingham for 11 years. She took a job at an English language school in Puglia, Italy, this month. “In the UK we’re set unrealistic targets and, compared to when I started, there’s little support. Things just get swept under the carpet.”

She left a previous school after she discovered a leader from the academy chain lurking in the corridor, monitoring her teaching through a window. “I felt I was constantly being watched.”

Her GP advised her to get a new job and, along with 11 other experienced teachers at that school, she did. But her new school was equally stressful. “Everybody was still under immense pressure. I love teaching PE, music and art and am passionate about languages. But in the UK, the focus is entirely on maths and English.”

After holidaying in Puglia, she decided to send her CV to all the language schools there and received three job offers. “I chose the one that seemed the best fit for me.”

On her last day of the UK summer term a parent yelled in her face. “I drove home from my final ever day in a primary school in this country in tears.”