What happens if you turn the notion of the school visit on its head and the gallery visits you? During the year of its closure for refurbishment, the Dulwich Picture Gallery, in south London, has been visiting schools and community groups, including young people in psychiatric care. It sends working artists to discuss the pictures in the gallery and teaches methods of drawing, the science of paints and pigments, or simply uses the pictures for storytelling.

Nick Ashton has been to Yattendon junior school, Horley, Surrey, to show the whole of Year 4 how to draw faces. He demonstrated how to scale a full face, three-quarters and a profile, how to measure with their thumbs on their pencils and how to keep looking at their sitter. “Artists are nosy!” he told them. “They must look again and again.”

The children soon became absorbed by their efforts. “Even Mark, who is usually fidgety, is engaged,” remarked his teacher.

Their first task was to draw the perfect oval; they folded their paper into four and saw that the bridge of the nose would be in the centre. “It’s hard,” said one of the girls, adding: “I’m going to practise at the weekend.” Nick showed them how to place the eyes and mouth, and soon they were drawing each other.

“You must respect your sitter,” he said. “You must be nice to each other to get a good portrait - the feeling comes through your arm.”

Headteacher Elisabeth Tope said that a visit like this “boosts and enhances what the children do in the classrom. They see a real-life artist like this and they can use them as a role model.

“It means so much for them to see things created in front of them.” And it advances their skills: “They can draw better than us!” she said.

Class teacher Joanne Oliver said: “A different voice, a different perspective, is very valuable. However much practice I’d done, I couldn’t extend the children this much.”

Nick was head of art in a south London school before he became a peripatetic representative of the gallery, so the business of motivation is familiar to him. “I always try to inspire confidence; that’s the key.” He remarked on the enthusiasm of the two junior classes. “Teaching young children is rewarding. There’s a willingness to try,” he said.

Some of the children were surprised by the visit. “It’s more fun than I thought it would be,” said one. “I thought we’d just be shown pictures.”

Leila said she was going to show her grandmother how to draw faces that very evening. Practising by drawing members of the family had been suggested by Nick - Leila extended it to teaching them.

Visits such as this are subsidised and cost schools pound;50 a day. Gillian Wolfe, the gallery’s head of education, says they like to customise the visits: portraits, myths and bible stories, the colour wheel, and investigations into the medium itself are all possible themes. “GCSE science classes can see how to make paint with egg white and chemical blue, and our science teachers have a collection of organic and inorganic artefacts.”

* Dulwich Picture Gallery, College Rd, London SE21 7AD, tel 020 8693 5254