Kate, 30, joined the youngsters from inner city backgrounds on a camping trip at the weekend.
Tigerlily Smith, eight, told the Daily Telegraph that the new royal chatted easily with them.
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"We asked her how it felt to be a Princess and she said it was very nice and she got to visit lots of countries but hadn't seen as many as William.
"She said William was very sweet and kind and spoilt her."
The excursion came after her appearance on Saturday with her new family, including the Queen and the Duke of Edinburgh, on the balcony of Buckingham Palace as part of the Trooping the Colour ceremony.
Of her royal duties Kate, dressed down in Zara jeans and £300 Le Chameau wellies, told them: It's very busy and great fun but I am very well looked after."
Many of the children from King Solomon Academy in Paddington, London had never been into the countryside before.
Their outdoor adventure was co-ordinated by ARK schools and supported by the Duke's foundation.
While his wife was at the retreat in Wrotham, Kent she sat cross-legged around the campfire and sampled food that the young people had cooked themselves.
Kate was also shown round the teepees by her eager hosts. One Zahid Shanvere, eight, held the flap open for her, saying: "After you". He earned a smile and the comment: "What a gentlemen".
On Monday, the Duchess was due to attend the Order of the Garter ceremony, before turning her attention to private celebrations for the Prince's 30th on June 21.
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