For years, school league tables have been all about academic results, with little attention paid to the feelings of the pupils taking the tests.

But now the Programme for International Student Assessment (Pisa) - which is responsible for the world’s most influential education rankings - is trying to shift the focus.

For the next round of the study, in 2018, officials want to include questions on body image in a bid to find out why teenagers - particularly teenage girls - are unhappy.

Mario Piacentini, analyst at the Organisation for Economic Cooperation and Development (OECD), which publishes the Pisa Students’ Wellbeing report, is clear that this is an educational issue.

“In some countries, beauty and thinness is emphasised more than in others,” he says. “Part of mental health and physical education should be learning about the risks of related to a narrow and problematic image of the self.”

There is evidence in Pisa’s last report on pupil wellbeing, published last month, which suggests that there may be a particular problem in this country.

Image problems

It revealed that the UK’s 15-year-olds were among the unhappiest in the world - coming 38th out of 48 countries - and that girls in this country were less happy than boys.

Pisa analysts believe that gender gap may be linked to body image. Their study also found that 36 per cent of UK girls skip breakfast, compared with 26 per cent of girls on average across developed countries.

Despite these findings, the UK is not signed up to take part in the 2018 body image research. Experts in the field are urging a change of heart for future studies. “Absolutely the UK should take part,” Natasha Devon, co-founder of the Self Esteem Team and a former mental health tsar for the Department for Education, says.

Bullying and test anxiety could partly be behind UK teens’ unhappiness, Pisa’s report has suggested - both of which were higher in the UK than almost everywhere else.

This does not explain why girls are less happy than boys. But previous research has shown teenage girls can be harsh self-critics of their bodies, prompting the Pisa team to investigate.

“In the next round, we will probably have some questions about body image and weight teasing, because we think this will explain part of the gender difference,” Piacentini says. “Body image problems exist among boys. But we know at that particular age among girls they are a bit more severe. There is research that shows this is related to an unrealistic and negative perception of the self.”

The arrival of Pisa (best known for its academically focused tables of maths, science and reading scores) into the arena of wellbeing is being welcomed by experts - but they urge caution on how the results are interpreted.

Helen Sharpe, lecturer in clinical psychology at Edinburgh University, has researched ways in which schools can help improve teenagers’ perceptions of their body.

“Inclusion of wellbeing and body image in a large international survey of this kind does highlight that young people’s mental health is increasingly being recognised as being central to what goes on in schools,” she says. “We have carried out research showing that poor body image in girls, in particular, is associated with feeling more sad or worried over time.

“It’s always worth bearing in mind, however, that some of this gender difference may be because boys are less likely to report difficulties even if they are not doing so well.”

The draft questions being drawn up, which offer respondents the option to strongly disagree, disagree, agree, strongly agree or have no opinion, include:

• I like my look just the way it is.
• I am not concerned about my weight.
• I like my body.
• I like the way my clothes fit me.
• I am always trying to improve my appearance.
• I usually spend a lot of time on personal grooming.

But the questionnaire will be an optional part of the study. The OECD says that eight countries have signed up to take part and that the UK has missed the deadline for 2018.

“We think the UK should have signed up,” Denise Hatton, the chief executive of the YMCA England and Wales, says. “Body image anxiety is a very real issue for young people, with more than half telling us they often worry about the way they look and more than a third agreeing they would do whatever it takes to look good.”

But the charity, which has campaigned to raise teachers’ awareness of body-confidence problems, wants to ensure the final questions pick up the complexities of how students feel.

“If someone doesn’t ‘like’ their body, it doesn’t mean they ‘dislike’ it,” Hatton says. “We would want to see questions proposed in the negative, for example: ‘I am unhappy with my body.’ This will give a definitive position of how unhappy the young people are.

“It will be from data like this that schools will be able to make positive changes to their environment, culture or teaching.”

But Devon points out that while schools can help, it is not necessarily their problem to solve. “Increasingly I have come to the conclusion that rather than sticking a body image lesson into the school, the curriculum has to change to put wellbeing at the heart of it.

“We as a society have to look at the kind of young people we want emerging from our education system.”

@teshelen