But Kate has revealed that she's since been well enough to do the school run with four-year-old George, and like many mothers, she hasn't always found it easy to leave him at the school gates.
The 35-year-old royal - who is currently expecting her third child with Prince William - was attending the Place2Be School Leaders Forum in London, during which she gave a speech detailing the difficulties some mothers face when their children start school to an audience of mental health professionals and teachers.
'As a mother just getting used to leaving my own child at the school gates, it is clear to me that it takes a whole community to help raise a child,' Kate explained (via Hello!).
'Whether we are school leaders, teachers, support staff or parents – we're all in this together. We are all working to give children the emotional strength they need to face their futures and thrive.
Kate is patron of Place2Be and spoke with experts at the event about how to provide support for children and nurture good mental health in young boys and girls.
We're all in this together
Mental health is an important issue both to Kate, Prince William, and Prince Harry. The royal trio lead the Heads Together campaign, which aims to stop the stigma surrounding mental health issues.
'Four years ago, when I became Patron of Place2Be, I believed what you all know to be true: that getting support to children at the very earliest stage helps improve their outcomes later in life,' she added at the event.
'Schools and teachers are at the heart of this support, and have a crucial role to play. You know your pupils.
'You know their circumstances. You can spot when a family's having a tough time. You occupy a special position because you can identify issues and take action when it's most needed. Parents also have a key role to play in this support system.'
Prince William recently revealed that Prince George was also struggling with being left at school too, but let's hope they're all finally settling into it now.