Children in England will be able to access mental health support in their school or college under Government plans to transform the treatment of mental illness in young people.
A green paper to be published on Monday will set out proposals to increase support and provide earlier access to services with £300 million in additional funding over the next three years.
Health Secretary Jeremy Hunt said the aim was to ensure mental health problems were identified and treated as early as possible to prevent them becoming more serious.
Under the plan, every school and college in England will be "incentivised" to appoint a designated "senior lead" for mental health to co-ordinate existing support services, as well as helping children access specialist therapies and other NHS treatments.
The senior leads will be responsible for developing a "whole school" approach to the issue - including ensuring pastoral support is available to all pupils and that effective policies are in place to tackle bullying and other behaviours which cause mental distress.
They will be backed by the creation of new mental health support teams to improve link-ups between schools and the NHS, and provide specialist support and treatments in or near schools and colleges.
Over the next five years, ministers say they expect to recruit "several thousand" people to the teams who could be trained to offer cognitive behaviour therapy and other treatments in the classroom.
The Government is proposing to provide £215 million over the next three years to fund the teams, with a further £95 million for the training of the senior leads.
Mr Hunt said: "Around half of all mental illness starts before the age of 14 so it is vital children get support as soon as they need it - in the classroom.
"If we catch mental ill health early we can treat it and stop it turning into something more serious."
In other measures, the green paper proposes:
:: Piloting a new maximum four-week waiting time for NHS children and young people's mental health services;
:: Ensuring every primary and secondary school in the country is offered mental health awareness training;
:: Commissioning further research into "evidence gaps" across children's mental health issues, including how better to support vulnerable families.
The plans were broadly welcomed by the Children's Commissioner for England Anne Longfield who said they represented a "step change" by the Government.
"Schools are the best place to make early intervention work and the best hubs for its expansion," she said.
"The question remains whether the funding that has been announced will be enough. We welcome what there is and will keep an eye on how this might be spent in the long term.
"There is no point having designated mental health leads assessing pupils that come to them, only to find if they need further specialist help, there is still nowhere they can be referred."
Dr Bernadka Dubicka, of the Royal College of Psychiatrists, said: "One of the biggest problems we see is that children who don't meet thresholds for mental health treatment often fall through the gaps. It is really promising to see the Government looking to tackle this.
"But it is crucial that there is enough resource available for the quality of care to remain consistently high."
For Labour, shadow health minister Barbara Keeley said: "This announcement leaves many unanswered questions, in particular whether the reported funding will amount to new investment and whether the incentives offered will lead to every school being able to offer proper mental health support to their pupils."