A qualified counsellor would be employed at every secondary school in England under Labour proposals to help young people live happier, healthier lives.
The party said the number of children experiencing mental health problems was increasing as it announced an additional £845 million per year for its Healthy Young Minds plan.
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Labour has pledged to recruit just under 3,500 on-site secondary school counsellors, and said it would ensure every primary school received a visit from a qualified counsellor at least once a week.
Labour said it hoped the proposals would enable the early prevention and identification of psychological issues, and ensure pathways to mental health support were accessible.
The party has also vowed to establish a network of drop-in, open-access mental health hubs to enable 300,000 more children to access support directly.
And it has pledged to develop and publish a cross-Whitehall national strategy to address adverse childhood experiences and trauma.
NHS data suggests one in eight 5- to 19-year-olds were diagnosed with at least one mental health disorder in 2017.
Labour leader Jeremy Corbyn warned that failing to help young people would store up problems for the future for a whole generation.
He said: "Almost every day, someone talks to me about the terrible stresses a child or young person they know are going through.
"Mental health workers do incredible work but our society is fuelling mental illness on a huge scale and our young people are not getting the support they need.
"As a country, we have to start treating mental health as seriously as physical health.
"If we don't help our young people, we are not only failing them but storing up problems for the future for a whole generation."
He said every young person "deserves the support they need for their talents to flourish and to play a full and positive part in the life of the community".
"Our manifesto will provide the real change young people need to live happier, healthier, more fulfilling lives," he added.
"Our Healthy Young Minds plan is a vital investment in the lives of our young people and an investment in our country's mental health."
Shadow health minister Barbara Keeley added: "The government is failing young people. Too many children can't access the mental health support they need.
"Our young people deserve better and our country needs real change to tackle the emerging major health crisis in children's mental health.
"Labour will ensure every school has a qualified professional on hand to support young people with their mental health, create a network of open access hubs for children to access mental health services without waiting months for an appointment."