A majority of teachers think exam results are prioritised over the wellbeing of pupils, a charity has said.
The government is being urged to tackle what has been described by YoungMinds as a mental health crisis in UK classrooms.
Most parents think schools have a duty to provide support for students' mental health, a survey by the organisation suggested.
Theresa May is being urged to redress the "fundamentally unbalanced" education system.
Pupils' wellbeing should be considered as important as academic achievement, the charity has told the prime minister in an open letter.
YoungMinds has called for proper funding of wellbeing initiatives, better recognition for schools that do good work on the issue, and specific mental health training for teachers.
The charity said 82 per cent of teachers agreed that the focus on exams had become disproportionate to students' wellbeing.
Wellbeing under pressure
A separate survey suggested that 92 per cent of parents felt schools should support the mental health of students, and three-quarters would choose a school that their child was happy in, even if its previous results were not good.
Sarah Brennan, chief executive of YoungMinds, said: "There is a mental health crisis in our classrooms.
"Children and young people today face a huge range of pressures, from exam stress to cyberbullying to finding a job when they finish education, and all the evidence suggests that the situation is getting worse."
She added that many schools do good work, but are often hampered by "competing pressures and a lack of resources".
"If the government is serious about tackling the crisis, it must rebalance the whole education system,” she said.
James Hollinsley, headteacher at Longwood Primary Academy in Essex, praised the charity's Wise Up campaign. "By formally acknowledging schools' efforts in pupils' wellbeing, and placing this on par with that of academic achievement, our nation will thrive," he said.
YouGov surveyed 810 teachers and – in a separate survey – 1,003 parents online earlier this year.