Self-harm, anorexia, aggression and bullying are the results of increasing childhood stress, according to a survey published today by the Association of Teachers and Lecturers (ATL).

Nearly three-quarters (73%) of the 804 teachers and lecturers believe children are under more pressure now than 10 years ago, with testing and exams, and family break-up causing the most distress.

Delegates at the ATL's annual conference in Torquay expressed concern at the increasing number of pupils across the UK who have killed themselves due to academic, social and peer pressure.

They urged the union to demand ministers co-ordinate work on suicide prevention and develop robust programmes for all schools.

John Harkin, headteacher of Oakgrove integrated college in Londonderry, said between 600 and 800 15- to 24-year-olds killed themselves each year - "equivalent to the population of a small secondary school".

He called the current suicide prevention strategy "piecemeal" and said mental health care was not available in all schools.

"Full access to mental health services is needed in all our schools not just the few ... it's like treating cancer with aspirin," he said.

Today's ATL survey found that while most children release the pressure by crying or becoming withdrawn, 46% of teachers reported that pupils self-harm.

Some have developed eating disorders, with 18 secondary teachers and two primary teachers commenting that there are increasing numbers of anorexia cases in their schools.

A secondary school teacher in Berkshire said: "Self-harm seems to be a growing problem. In my first 30 years of teaching I was aware of only one case. In the last eight years, there have been at least 10 cases. The youngest pupil I know is 14 years old.

"Pupils cut their arms and even their stomachs. It's not just girls, but boys too. Some say that if they hurt themselves in other ways, then they don't hurt so much from what's really causing the pain. I also know three or four cases of anorexia in the school brought on by stress."

Other manifestations of stress include: crying (reported by 76% of respondents); withdrawal (70%); aggression against other pupils (68%); verbal abuse (64%); bullying other pupils (53%); and fighting (48%).

Most teachers (89%) think stress comes from testing and exams, with family break-ups (68%) and peer and family pressure to do well (51%) also the main causes of problems. The recent phenomenon of cyber-bullying as a cause of stress was highlighted by 38% of teachers, compared to physical or verbal bullying (26%).

Phil Walley, of Hardenhuish school in Wiltshire, said social dysfunction had potentially disastrous effects on pupils' education achievement.

He said: "Those who underachieve in their education are much more likely to go on and live dysfunctional lives and be unable to support a stable family life for their own children.

"As a society we are in danger of creating an expanding, perpetuating and toxic circle. If we are not careful we could reach that crossover point where no matter how hard schools and teachers try, they will not be able to overcome the negative impact of broken and dysfunctional families."

According to ATL's survey, 72% of teachers said their school has a policy to identify pupils with problems, and 74% have a counsellor. But only 18% of teachers thought support services were well co-ordinated.

A secondary school teacher from Bristol said: "I am dealing with three pupils at the moment with mental health issues and many more face stress, mainly from family dysfunction and exam pressure, with pupils showing signs of withdrawal and inability to learn."

Mary Bousted, general secretary of ATL, said: "The recent shocking spate of teenage suicide has focused attention on children's mental health and wellbeing.

"We believe that young people face intolerable strain from an education system which cannot stand failure. From an early age, children face the pressure to perform in tests to boost their schools' league tables.

"Then they take on parental demands to get into their choice of secondary school and later university. They are anxious to fit in with their peers, and then when they don't fit in, are bullied via text, email and social networking sites."

Local support services were "alarmingly" over-burdened and teachers were forced to "pick up the slack", she said.