William wore safety glasses and gloves to saw through a log, held steady by the Princess whose right hand was still bandaged from a trampolining injury.
“Is William doing it right?” she asked the youngsters, who told her he was.
She politely declined the offer of gloves for herself, saying: “I can’t even put that on because I’ve got two fingers stuck together.”
The future King also tried his hand at whittling, taking tips from Jake, 10, on how to use the knife.
Admiring a stick Jake had worked on, he said: “Is this yours? It’s brilliant.”
Headmaster Lee Batstone explained that children burn the names of reception children onto the sticks back at school and they use them as part of their registration process each day.
New starters and their parents also receive wooden heart-shaped discs with the school motto “Be the best you can be”, which are placed in their hands and kept throughout their time at the school.
William and Kate were presented with three to take back home for Prince George, Princess Charlotte and Prince Louis by Lucy and Tomas, both 10, along with three books on mindfulness.
The couple also joined pupils under a canopy made from a parachute where they were making apple, cinnamon and sugar skewers to toast on a fire.
“It’s like a healthy marshmallow,” said Kate. “It always tastes so much better whenever you cook something on the fire.
“I’ve seen 1,000 marshmallows around the fire but I’ve never seen a sugar-dipped apple. I’m going to try this with my kids.”
“It smells delicious,” added William.
She was told children learn how to start and maintain the fire from Year 6.
“These are really good skills to learn, to be able to keep warm, to feed yourselves,” said the Princess.
“Is it nice learning here? It’s so peaceful, isn’t it? I could stay here all afternoon.”
All pupils attend the outdoor school at least once a week and learn national curriculum subjects along with awareness of the environment, conservation and woodland management.
The sessions include time in a mindfulness circle where the canopy overhead forms the shape of a heart and hide and seek during playtime.
The school, which has five fully trained forest school leaders, is partnered with the Duchy of Cornwall, which provided it with the woodland site at Brampton Hill Wood 12 years ago.
It was the idea headmaster Gareth Batstone and Geraint Richards, Duchy Head Forester.
The youngsters learn about building things from natural materials and how to use knives and equipment safely and correctly.
William inherited the Duchy of Cornwall when he became Duke of Cornwall on the death of Queen Elizabeth II.
Valued at more than £1 billion, the estate covers 23 counties in England and Wales, including large holdings in Herefordshire.