The word yoga comes from the Sanskrit root yuj, and means to link or unite.
A reunion with the universe, or with one's true self, is sought by those who practise it. With the stresses of the coming term for children and teachers -tests, reports, self-evaluation - the chance to calm down and sense the broader picture holds some appeal.
Yoga for children has taken off in the general community, at least among the middle classes, so it is not surprising that schools are beginning to embrace it as well. Parents argue that what works for them must work for their children and, of course, for the kids there's that celebrity hook.
"Children see how many celebrities have shown they can build strength and flexibility", said Andree Deane, director of the Fitness Industry Association, which surveyed children to find what activities they wanted.
She adds: "Taught correctly, yoga can be very beneficial. It also leads to good posture, which is very important."
The association has received government funding for its members to pair up with schools to offer 10 and 11-year-olds sessions like those it provides for gym members. This is an area where passions run deep. "It's not really yoga," practitioners will say about what is being taught to children on the other side of town. And certainly classes for younger primary children bear little resemblance to adult classes.
A recent after-school class for reception pupils at Baddow Hall infants school in Chelmsford was set in the jungle. "Imagine you are a seed," says teacher Sarah Sadler. "Come down on your knees; head down." The children do as she says, then as "the sun comes up" they stretch up. They then stand on one leg with both arms raised like a tree, in fact a tree pose is what it's called in an adult class. The children then follow a little red monkey as he meets a crocodile, a snake, a lion and an elephant, each of which has its pose.
The tale is a moral one, of thoughtlessness repented. The poses and breathing exercises form part of the story-telling session, though sessions for older children more closely resemble those for adults. But in both there is no straining and very little correcting of postures.
The session ends with relaxation: children lie down and imagine the jungle.
Then Ms Sadler talks about how to use one particular exercise when you feel angry.
Yoga may improve flexibility and posture, but it's the way it relaxes children stressed out by Sats and soothes hyperactive youngsters that teachers talk about. If they have or are considering incorporating it into the curriculum, often it is in personal, social and health education, not PE.
At Gearies infant school in Redbridge, yoga is part of the PSHE curriculum.
"We wanted to give pupils the skills to help them manage their own emotions more," says headteacher Bob Drew. All Year 2 children take yoga during the autumn term, "because the school found that was when behaviour began to deteriorate. The children are much calmer after they've started." He would like to extend yoga, "but we can't afford it".
Michael Chissick, a teacher at Gearies, has been trained by the British Wheel of Yoga, the UK governing body. Through his organisation, YogaBuds, he is training his first cohort of teachers in a Btec advanced diploma to teach yoga in schools. He uses stories to link postures and ties yoga to curriculum topics.
Another concern is that yoga manoeuvres are primarily designed for adults.
Can we be sure they are suitable for children? There is controversy around even this basic question. The American Yoga Association suggests that children may safely practise yoga, meditation and some simple breathing exercises to help them relax and concentrate, but doesn't recommend yoga exercises for children under 16, arguing that they may interfere with growth.
The Iyengar Yoga Association, which advocates a very disciplined form, does not take children under seven. "A child's head is bigger in proportion to his or her body before seven and the big muscles which help stability have not developed," says Iyengar yoga teacher Korinna Pilafidis-Williams, adding that "standing poses and especially jumping build up their bones".
But many groups, including the British Wheel of Yoga, run courses for children. Sarah Sadler, teacher at Baddow Hall, teaches a type of yoga aimed at three to seven-year-olds, developed by YogaBugs. Around 500 YogaBugs teachers now teach in nurseries and schools.
The organisation shows them "how to adapt postures to the various age groups," says founder Fenella Lindsell, and they "are totally safe." She adds that "yoga for young children is a magical way of introducing them to fun, creative adventures".
But yoga demands a lot of teachers. As Sue Chedzoy, director of physical education at Exeter university school of education, puts it: "The value of yoga depends on how it is delivered, who is delivering it and how much they know about the physical, emotional and social development of children."
www.yogabugs.comwww.yogabuds.org.ukThe British Wheel of Yoga: www.bwy.org.ukThe Iyengar Association: www.iyengaryoga.org.uk