More children have mental health issues than two years ago, a survey of school teachers suggests.
More than half of 850 staff surveyed by the Association of Teachers and Lecturers (ATL) agreed more pupils had developed problems.
On Monday, the ATL's annual conference will debate a call for more support for vulnerable pupils in schools.
General secretary Dr Mary Bousted blamed "poverty, poor housing, unemployment and financial insecurity".
School staff have had to "plug the gaps in social care as best they can", said Dr Bousted.
Some 861 ATL members responded to the survey earlier this month.
More than one in six said they believed at least a quarter of students in their school or college were affected by mental health problems.
Almost 90% said staff have had to provide more support for these pupils over the past two years, while 43% said they had been finding it harder to access services for pupils with mental illness.