A groundbreaking research project is to be launched to help teachers deal with pupils who have special educational needs (SEN) and mental health problems.
Studies have long suggested that children and young people with SEN are at greater risk of developing mental health problems, but teachers often struggle to separate the two issues.
"There are many children in special schools with mental health disorders that have no diagnosis whatsoever," said Professor Richard Rose, director of the Centre for Special Needs Education and Research. "It is extremely difficult to expect teachers to detect any neurological problems beyond the special educational needs."
Professor Rose will lead research, in partnership with the National Association of Independent and Non-Maintained Special Schools (NASS), to improve SEN teachers' understanding of mental health.
There is currently no guidance for teachers on how to address the problem.
Claire Dorer, chief executive of NASS, said: "Children and adolescents are always more vulnerable when growing up, but on top of all this children in our schools have other special needs.
"Anxiety and depression are issues we know about to a great extent. But we don't know, for example, how to get an autistic child to express depression."
The Count Us In inquiry in 2001 estimated that 40 per cent of young people with disabilities have mental health problems. In 2004, the Office for National Statistics said a child is six times more likely to develop a psychiatric disorder if they have a learning disability.
The research, which begins next month, will be carried out over two years in 12 independent and non-maintained special schools across the country.
"These teachers are extremely skilled and competent but they are not equipped to deal with mental health issues," Professor Rose said.