The first day of school can be stressful but Princess Charlotte will have her older brother there to lean on.
The fee-paying school has 560 students between the ages of 4 and 13 and seeks to produce "caring citizens of the world," according to its website. It reportedly costs $24,000-a-year and is only a few miles away from the family's Kensington Palace home.
Headmaster Simon O'Malley said the school is "delighted" that Prince William and Kate, the Duchess of Cambridge, have chosen their school for Princess Charlotte.
O'Malley said, "We greatly look forward to welcoming her and all of our new pupils to the school in September."
Princess Charlotte previously attended Willcocks Nursery School, which she started in January 2018. Prince George has been at Thomas's Battersea since September 2017.
This week, the British Royal family shared some photographs of their trip to the BHS Back to Nature Garden at the Chelsea Flower Show. George, Charlotte, and baby brother Louis played in the water and on a swing under the close eye of their parents
The Duchess of Cambridge, Kate Middleton, said of the day, “I really feel that nature and being interactive outdoors has huge benefits on our physical and mental wellbeing, particularly for young children."
"I really hope that this woodland that we have created really inspires families, kids and communities to get outside, enjoy nature and the outdoors, and spend quality time together," she added.
The AP contributed to this story.