School guidance counsellors say they are increasingly stretched by students' mental health needs and the impact of the recession on poor communities.
A new report by the Education Review Office says many counsellors are so busy they are not able to work proactively or safely.
The review office surveyed 180 counsellors, most of them at secondary schools.
Sixty-nine percent said their job has changed because of the increased frequency and complexity of students' mental health needs in the past five years.
The report says that change, and the impact of the recession, means there is more demand for counsellors' time and schools are finding it harder to access help for their students from external agencies.
Low resourcing means they are unable to work proactively or safely, and six of the counsellors say they are functioning at crisis management level.
Three-quarters say lack of time is their biggest challenge. They say there are not enough of them to deal with rising mental health and family problems among school children.
Govt needs to fund more counsellors - association
The Association of Counsellors says the Government needs to change the staffing system.
Spokesperson Sarah Maindonald says schools need more counsellors to help students with an increasing number of problems.
"Prior to 1995 there was a tagged position of one counsellor to 400 students, which would avoid the kind of high caseload and potential burnout situation we have at the moment, where some counsellors have a school population of 2000 students."
Ms Maindonald says the rise in demand for counsellors' help could be because students feel more comfortable going to them than in the past.