Pupils from Stanley Grove Primary and Nursery School have received a letter from Kensington Palace after making Prince George a guide on being a big brother.
Year five pupils sent congratulatory messages to the Duke and Duchess of Cambridge to celebrate the birth of Princess Charlotte in May.
And they also made a book for the young Prince, aged one, advising him how to be “the best big brother in the world”.
The creative nine and ten-year-olds designed the book with words and pictures suggesting he helped clear away her toys and showed her how to brush her teeth, among other tasks.
The class was surprised to receive a letter back from the palace, sending “warmest thanks and best wishes” from Prince William and Catherine.
It said: “Their Royal Highnesses have been overwhelmed by all the incredibly thoughtful messages and were immensely touched that you and the year five children should take the trouble to write as you did.
“The Duke and Duchess were heartened with the care the children have taken to make the splendid picture book especially for their son, Prince George, and they appreciated the kind words of support for him.”
Each child also received an individual thank you card.
Class teacher Joanne Kershaw: “On the day we got the reply, the children all shot out the classroom at the end of the school day waving the cards for their parents to see.
“We didn’t expect to get a reply that quickly so it was really nice for the children to have that.
“We were all very excited and the children really appreciated getting an individual response.
“We shared these with the whole school during a special celebration assembly.”
She added that the birth of the little Princess, whose full name is Charlotte Elizabeth Diana, on May 2, presented “a lovely opportunity to provide a real purpose for the children’s work.”
Princess Charlotte of Cambridge is fourth in line to the throne, behind her grandfather Prince Charles of Wales, father Prince William and big brother Prince George.
The two-month-old was christened at St Mary Magdalene Church in Sandringham, Norfolk on Sunday in front of the Queen and close family. It was the Cambridge’s first public appearance as a family of four.