Yoga has long been used to relieve stress and improve posture. Now the benefits of the ancient discipline are being used by schools to improve concentration and help relaxation.

By 2007, the child yoga specialists YogaBugs estimates that at least 100,000 children will be taking part in classes each week, double the number practising yoga last year.

Fenella Lindsell, founder of YogaBugs, which teaches children from the age of two to 12, said: "It improves children's co-ordination and balance, builds strength and stamina and promotes healthy sleeping patterns. Yoga is also valuable for pre-teen children who go through an enormous amount of physical, mental and emotional changes."

A spokesperson for The Yoga Show, at the Olympia centre in London this weekend, said they are holding more children's classes this year than ever before.

Karen Conroy, headmistress at Norfolk Lodge Nursery and Preparatory School in Barnet, north London, said teachers have found that yoga introduces "a pocket of calm" into classes. She said three- and four-year-old children spend 15 minutes doing simple deep-breathing poses after their lunch break. The school has adopted an approach that puts each yoga posture to music, named June's Yoga after founder June Rowlands. So while children are stretching into the triangle pose (Trikonasana), they will sing "I'm a little teapot".

Ms Conroy said: "It is a very friendly approach to yoga, with rhymes that the children already know, such as 'Row, Row, Row the Boat'. They find it fun, and the teachers find it useful in helping children to concentrate in class, giving the younger children the experience of calm and control."

Georgie Wolfinden, a wellbeing expert, said: "Children are more stressed than before and have forgotten the importance of how to play. Yoga gives them some space to be calm and creative and just be kids again.''

At Northbridge House School, yoga teacher Susie Paterno has found that children learn the poses very quickly. "Children can do all the postures without difficulty," she said. "It also helps them to sleep better and concentrate in class."

Robin Cacco, who teaches children's yoga at the Triyoga Centre in London, said that children make animal shapes in his classes. But while the children believe they are going on an adventure, they are learning skills that help them to cope with the more academic of school subjects.

Ms Lindsell said: "It helps to improve self-confidence and enables children to deal with the stresses of exams and school performances."