Kate visited Roe Green Junior School in Brent to announce a pilot initiative for the Heads Together campaign.
Mentally Healthy Schools, a new website, is designed to help teachers talk to children about issues ranging from bereavement to anxiety to eating disorders.
The website is designed to suit primary schools in England and includes more than 1,500 online resources.
It has been checked by a “quality assurance group” to make them appropriate for a young audience.
Kensington Palace said: “Teachers and staff play a pivotal role in a young person's life, but they currently struggle to find the right resources in order to provide the most effective support for children in their care.
“Up until now, the array of online resources has been difficult to navigate; it is often unclear whether items are expertly verified, and teachers are often unsure how appropriate the advice is for their particular age-group or issue.”
Pregnant Kate, mother to Prince George, 4, and Princess Charlotte, 2, and who campaigns on mental health and young people, has spoken regularly about the importance of good mental health in children.
She has previously told young people via a charity video: "It helps us all talk about our mental health, what to say and who to talk to when we have feelings that are too big to manage on our own, and how to listen and help if one of our friends is finding things difficult.”
Supporting the You're Never Too Young To Talk Mental Health campaign by the Anna Freud National Centre for Children and Families last year, she said: “As parents, we all want our children to have the best possible start in life.
“Encouraging children to understand and be open about their feelings can give them the skills to cope with the ups and downs that life will throw at them as they grow up.”
Sarah Hannafin, senior policy advisor at school leaders’ union NAHT, said of the project: “School leaders have been clear that they need access to high quality resources to help schools’ work in supporting children’s mental wellbeing.
“This new website will be a fantastic practical resource for schools, drawing together quality assured and useful information and resources into one place. We’d encourage all primary school leaders and their teams to bookmark it.”
The Heads Together campaign is jointly co-ordinated by The Duke and Duchess of Cambridge and Prince Harry, with the aim to end stigma around mental health in the UK.
The project is a partnership between several charities including Contact, a collaboration of military support organisations; YoungMinds, a charity that helps children and young people suffering from mental health problems; and Best Beginnings, which supports the mental health of pregnant women and new mothers.
Heads Together is the 2017 Virgin Money London Marathon charity of the year and is hoping to change the national conversation around mental health.