Schools are struggling to cope with increasing numbers of pupils with mental health problems, a study says.
Increasing number of children suffer mental health problems
The survey commissioned by the NASUWT teachers' union found teachers often had difficulty identifying pupils with problems like anxiety and depression.
Inadequate support for teachers affected the well-being and school work of other pupils in the class, it found.
The NASUWT wants to see more training for teachers in how to deal with the children concerned.
The report concluded that information about pupils' problems were not being shared between schools, or even within schools.
And teachers who deal with the needs of pupils with special educational needs (Sencos) told researchers they received no specific training on mental health.
The study was conducted by the research department at Barnet, Enfield and Haringey Mental Health Trust in London.
"Teachers are concerned about the impact arising from the inadequate support of pupils with mental health needs," the trust's report said.
"There are repercussions for the child who needs the special provision.
"Teachers believe they cannot meet the child's needs, provide them with equal opportunity, help them achieve their potential, or help them before their problems become so serious that they will impact on the rest of their lives."
The report warned that this also had "a powerful and detrimental impact on teachers".
"It can make their job very difficult, lower their 'job satisfaction' and more importantly is likely to affect their own psychological well-being.
"In addition, teachers argue that inadequate support negatively affects other children whose education and mental or physical well-being may suffer as a result of that particular pupil's behaviour."
A spokesman for the Department for Education and Skills said they had already delivered specialist training to staff who have particular responsibilities for children with behavioural, emotional or social difficulties.
"We are also looking to develop targeted support for more schools to help them identify and tackle behavioural problems due to mental health, including referral to more specialist help," he said.
The department said it was working to expand Children and Adolescent Mental Health Services so that more specialist help and advice was available where needed.