The royal mum-of-three sat down on a log next to an excited group of youngsters for story time. One little girl, Anwaar, left the royal in a fit of giggles after putting on a playful display.
Kate watched with amusement as the four-year-old cuddled her and attempted to drink from her cup without using her hands.
Simon Atkinson, the London school's headmaster, had been chatting all day about meeting "the princess."
He laughed, telling PEOPLE, "It was clear that nothing was going to stop her saying hello!"
An onlooker told PEOPLE, “She was calm with the children.”
During Tuesday’s event, Kate got down in the grass with a young student as they hunted for “mini beasts,” but they could only find slugs.