Four out of five head teachers in England are concerned about pupils in their schools suffering from anxiety disorders, a survey finds.
A poll of more than 1,000 heads by the school leaders' network, The Key, found 64% saw pupil depression as a concern.
In total, 80% of secondary school heads expressed concern about self-harming.
The Key says delays in getting young people referred to the Child and Adolescent Mental Health Service (Camhs) is of particular concern.
The survey of 1,131 head teachers also found:
- 41% expressed concern about eating disorders among pupils in their school (32% in primary schools and 55% in secondary schools)
- 51% expressed concern about self-harm among pupils in their school (33% in primary schools and 80% in secondary schools)
- Of those who made a referral to Camhs, 45% had to wait between one and three months for the case to be followed up, 26% had to wait three to six months and 9% had to wait more than six months
Amy Cook, senior researcher at The Key specialising in pupil well-being says: "The impact of council budget cuts on Camhs means that the job of nurturing pupils' mental health is increasingly falling to schools.
"And since our ability to take in new information can be significantly affected by our mental health, it's not an issue that teachers can ignore.
"These figures emphasise both the current strains on the mental health system and the pressures felt by school staff, many of whom don't always have the means or training to properly address these issues."
Provision of mental health services for young people varies widely across England, with entry-level care largely funded by local authorities which are facing budget cuts.
According to research by the charity Young Minds, more than half of councils have cut or frozen budgets for child and adolescent mental health.
Mental health services account for 10% of the total NHS budget, with just 6% of this earmarked for Camhs, it says.
Responding to The Key poll, Lucie Russell, director of campaigns at the mental health charity Young Minds said: "Sadly, these figures are not a surprise.
"Schools tell us they want more mental health support to help provide care for their pupils. With cuts to children's mental health services up and down the country services are really struggling to cope with demand.
"Mental health spending needs to be prioritised, it is a national disgrace that just 0.6% of the NHS budget is committed to Camhs when statistically three in every classroom will have a diagnosable mental health problem."
The Local Government Association (LGA) said councils were overstretched and it wanted to see a "complete overhaul" of the system.
David Simmonds, chairman of the LGA's Children and Young People Board, said: "Councils have worked hard to protect the many services they provide for vulnerable children but in the face of 40% cuts to local government, this has becoming increasingly challenging.
"Local authorities have serious concerns about mental health funding for children and want a complete overhaul of the fragmented and complex system that they currently face each day when trying to access services delivered by the NHS and other partners.
"It is absolutely crucial that the whole system is properly funded, resourced and joined up to ensure young people receive the very best services available."
The Key, founded in 2007 as part of a government-funded initiative to support schools in England, brings together school leaders from across the country to share practical ideas and experience.