The Association of Counsellors warns school counselling services are badly over-stretched and need more funding from the next government.
The association's president Sarah Maindonald said a Council for Educational Research study that found support for vulnerable students is an issue for 80 percent of secondary principals was "absolutely" accurate.
Maindonald said school counsellors were struggling to keep up with demand from students seeking help for problems, including anxiety and depression.
"As an association we've been very concerned about the mental health of secondary school students for many years and we have lobbied the government to increase the staffing and tag the staffing so there's a counsellor available in every school in the country.
"We're looking to have a ratio of one counsellor to every 400. At the moment it's very inequitable across the country. Sometimes there's a counsellor for every 1400 students and one to 2000 which is actually a risk."
Maindonald said research showed school counsellors were an effective way of supporting young people's mental health. She said children and teenagers were more likely to seek help from counsellors if they were based in schools.
"A counsellor employed by the school is part of the school community, so students build up a trusting relationship so when they're dealing with a crisis they can access help.
"Students actually have identified school counsellors as their number one go-to for mental health, sexuality, drink and alcohol, and family violence issues. So they're critical supports for young people."
Maindonald said school pupils often sought help for problems including grief at the death of a family member, peer relationships and parents separating, but since Covid-19 counsellors were seeing more cases of anxiety and depression.
She said she used to work in a Christchurch school where the cumulative effect of the city's earthquakes, the mosque attack and Covid-19 was dramatic.
"Our case load went up about a third. It went from 60 to 90 a term at the time I was counselling in a school and it went up to 90 to 100 and it never came down. I thought it might come down in a couple of years and it just didn't."
She said counsellors were leaving the profession because of the rising stress of their job.
Maindonald said she hoped the next government followed through on commitments to improving mental health services and did not get sidetracked into exploring alternatives.
"It's really simple. To have universal access for counselling in schools you add counselling to staffing and you tag it," she said, explaining that would ensure the funding could not be used for other purposes.
"If the government tagged counselling to staffing with a ratio of one to 400 that would make a real difference for youth mental health."
Maindonald said it would cost about $66.5 million to bring the number of school counsellors to 700 and meet the 1:400 ratio.
She said secondary students needed skilled professionals because they were at a vulnerable stage developing their identity with increased risk-taking behaviour.