Teachers who are happy in their jobs achieve significantly higher academic results from their students than colleagues who are suffering from stress, academics have found.
According to researchers from the Work Foundation at Lancaster University, the well-being of staff makes a marked difference to students' exam grades and should be a focus of national attention in order to tackle pupil underachievement.
Teacher happiness can make an 8 per cent difference to students' exam grades in both primary and secondary schools, according to the research review.
"This is an important finding," the study states. "Unlike other factors, such as the social class of students, the rate of pupil absence and the number of children with special educational needs, teacher health and well-being may be more amenable to intervention and change."
Other studies cited by the academics show that teacher happiness has a significant effect on students' emotional adjustment, and that this also has an impact on their academic achievement.
"If you're not particularly engaged in a task that you're doing, you have a why-should-I-bother attitude," said Dr Zofia Bajorek, who led the research. "But if you're really engaged with your work, if you really love your job, you'll do the best you can to be successful."
The Work Foundation study, commissioned by the Teacher Support Network, will be launched on 8 September. The charity, which runs a 24-hour helpline for teachers struggling with stress and emotional strain, is calling for a renewed focus on teachers' health to produce more effective schools.
"People forget how complex teaching is, the needs you're spanning in a class of 25 or 30," said Julian Stanley, chief executive of the Teacher Support Network. "Unfortunately, health and well-being have been seen as fluffy, woolly kinds of things. But, actually, we need to take them seriously."
One study reviewed by the academics surveyed more than 24,000 members of staff in 428 primary and secondary schools, finding that teachers' happiness accounted for an 8 per cent swing in test results.
Another report cited by the Work Foundation study states that 89 per cent of teachers find their job at least moderately stressful. Fifty-eight per cent believe that excessive stress at work compromises their physical or mental health.
In recent years, significant national attention has been paid to improving student well-being, with advocates arguing for the need to build resilience and "character", so as to create well-rounded children and improve their academic performance.
Sir Anthony Seldon, known for introducing "happiness lessons" to the curriculum at Wellington College in Berkshire, said student and staff satisfaction were, in fact, the same thing. "If a teacher is optimistic, if they instil that sense of optimism and belief in their students, it's inevitable that the students will do better," he said. "For students to do well, they need to have relationships in lessons which are positive, enjoyable.
"If you have a negative, cynical, grumpy, exhausted, frightened teacher, the students will not enjoy going to their lessons. They might induce fear, but they're not going to engage with the young people. It's about making the teachers feel rewarded themselves - that they're part of a great school. That there's a sense of excitement and a sense of travel, journey."
In the 2012-13 academic year, 57 per cent of teachers took at least one period of sick leave, an increase of 2 per cent on the previous year. The average number of days lost per teacher was 7.9.
Sue Wickstead, who taught at a primary school in Sussex before being signed off with stress, said: "When teachers are under stress, the children pick up on that, and if teachers are off ill you've then got a class with no teacher. One minute the teacher is there and the next they're gone. You can see the children are worried. And those children are having to put up with a constant stream of supply teachers."
Andrew Oswald, professor of economics at the University of Warwick, said there was clear evidence that students' results suffered when their teachers were persistently absent. "This means we need, as a sensible society, to make sure that our teachers want to come to school and are psychologically well enough to come to school," he said. "Happy teachers produce successful pupils."