The announcement has been made just ahead of the family moving out of Kensington Palace for a new home on the Windsor Estate.
The relocation from central London to Berkshire has been driven by William and Kate so their children can have more freedom.
All three have lived at Kensington Palace since they were born.
Prince George, a future king, has been a pupil at Thomas’s Battersea school since 2017.
His sister, Charlotte, has also been going to the same school since 2019.
Their new school, Lambrook, takes children from ages three to 13.
George and Charlotte will be in the prep school whilst Louis will attend the pre-prep school.
Lambrook is set in 52 acres of grounds which will allow the Cambridge children to do much more of their learning outside - something Kate had focussed on in her Early Years work in recent years.
The school website say it encourages outdoor learning by giving them the chance to “explore, play, learn and of course, to get muddy!”
Prince William and Kate are relocating the family to Adelaide Cottage in Windsor Great Park in the coming days although their office and staff will remain at Kensington Palace.
The couple want their children to have a more private childhood and feel that Kensington Palace, in the middle of Hyde Park, does not give them the privacy they need.
Their staff say the Cambridges sometimes feel like they are living in a “goldfish bowl”.
The palace is overlooked on many sides and means the children risk being photographed by paparazzi or members of the public if they play too far from the main building.
Adelaide Cottage is smaller than Apartment 1A at Kensington Palace where the family have been living.
The four-bedroomed property means they will no longer have a live-in nanny. The children’s nanny, Maria Borallo, will continue working for the family but will no longer live with them.
The house, owned by the Crown Estate, was famous before William and Kate‘s arrival there.
It was once home to Group Captain Peter Townsend, the man Princess Margaret, the Queen's sister, famously fell in love with but could not marry.
Royal sources say the move to Windsor is not connected to the Queen's frail health.
The Monarch, who is 96, it’s currently in Balmoral for the summer but spends most of the year living at Windsor Castle.
William and Kate have no plans to move into the castle itself.
Their move to a house on the Windsor estate means they will be living very close to Frogmore Cottage, which remains Harry and Megan‘s official UK residence.
The Duke and Duchess of Sussex announced last week that they will be returning to Britain in September for a series of engagements.
They retained Frogmore cottage and agreed to keep up the rental payments on it since they left for California in 2020 when they quit as working members of the royal family.
Given the continued strain in the relationship between the brothers William and Harry, they are unlikely to see very much of one another when Harry and Megan are back in the UK - despite the new living arrangements.
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