PLAYGROUP is over. A line of grubby three-year-olds march out, clutching pieces of sugar paper decorated with splodges of poster paint. All except your child, who spent the morning playing with toy cars.

'Didn't you make a picture?' you ask. He hangs his head. The other children hand over their masterpieces and you try to hide your irritation. It's not doing the painting that matters so much as the bringing it home, having something to show for a morning's work. There is the feeling that, without a trophy or something to stick on the fridge door, your child has let you down.

After all, isn't this why we send our children to playgroups - to learn something, and to bring us back a memento of their achievement? This seems to be the thrust of government policy on testing in schools: that it is not enough for our children to be working things out for themselves, or to be logging up experiences in their own heads and hearts. We demand tangible results, we want to check what is inside their heads. We want control.

Growing up never used to be like this. It was something you got on with, something that just happened, something you worked out with your friends. Apart from school, a child's time was generally his or her own. Homework was a minority pastime, reserved for those heading for their final exams. Early education was unheard of. Twenty years ago, children grew up without mini-gym, tumble tots, Crechendo, Club Francais or computer group. The nearest you could get to an extra-curricular activity was Brownies or being in the school hockey team. Even then you were likely to choose one or other activity, not both.

These days, we are less inclined to let our children loose than any parents before us. A generation who scraped their knees climbing trees have grown up to be chauffeurs, ferrying the kids to short tennis, mini-rugby, or some other scaled- down version of adult sport. No one climbs trees any more.

This is supposed to be an advanced state of child-rearing, but I wonder what good and how much damage is being done when we commandeer children's time and energy. It occurs to me that when we over-organise our children's lives and demand evidence of their success, we are disturbing a precious mechanism. Have we forgotten what the musician, teacher and philosopher Sinichi Suzuki called 'natural growth'?

'A seed is planted in the earth,' he wrote in his book, Nurtured by Love. 'We don't see when the germination begins. That is the doing of Mother Nature; it is the fundamental working principle. We have to wait patiently. We cannot dig up the seed to see whether it is really growing; to do so would be to destroy everything.'

There is a world of difference between self-initiated play and adult- organised activity. Children may benefit from the second, but they desperately need the first in order to thrive. When a grown-up organises a game of football, children learn to obey an external set of rules. When children play by themselves, they learn to make minute judgements of their own, take responsibility for their actions, opt in and out as they feel fit, hone their physical and social skills and - perhaps most importantly - exercise their self-motivation.

At a recent discussion group in London, parents talked about the phenomenon of child burn-out. A number reported seven- and eight-year-olds who suddenly refused to attend another ballet lesson or swimming class. 'My daughter has just had enough,' said one mother. 'There was me worrying about whether she should take on a musical instrument, and she was already burnt out. I began to think, what does it matter if your child can do a somersault on the trampoline by the time she's seven? You get so caught up in all the options, you forget they are only children.'

'The world is your oyster,' we tell each new generation, but a diet of oysters is too rich and unmanageable for small stomachs. It is hardly surprising if children are starting to rebel. They need time to stop, to sit this one out if needs be.

Take day-dreaming, an activity likely to move even the mildest teacher to sarcasm. All children need time to stare. Researchers have found that the brightest children are those who have been allowed to stare without interruption, and this may be the time when mental concepts are roughed in. But a child who sits gazing out of the window is likely to be woken from reverie and begged to join in, or do something 'worthwhile'. We think nothing of disturbing our children's time, which - in the long span of life - ought to be the one thing they have on their side.

Time is a rare commodity for the modern parent. In the 1980s, with the increase in opportunities for women in the workplace, we saw the invention of Quality Time, in which a parent aims for intensive, positive relations with a child in the space between work and bed. It is a system doomed to end in tears. As one mother put it: 'I would be tense during the entire drive home from work, thinking 'I must relate with Emma, I must relate with Emma.' But when I arrived home, Emma would want to watch television.'

This is not an argument for mothers to ditch their briefcases and sit at home ogling their offspring. It is, however, another indication that children do not relish any intensive input. A great deal of positive interaction is, in any case, very wearing for all concerned.

This realisation can come as a great relief to parents who worry about how to fill the day with their children. 'Parents who spend a lot of time away from their children often find they have lost the knack of just being around them,' confided one working mother. 'You feel you have to do something with them. I have even heard of working parents getting a relief nanny at weekends, so they don't have to face amusing the children all day.'

But the children do not want to be amused. Give them a box or a back garden and they are perfectly equipped to amuse themselves. Unless they have forgotten how to.

Nor are they much interested in amusing us. If they paint a picture or tinker on the piano, they do not do it for the final framing or for the glory of Carnegie Hall. We can never hold our children up and say 'Look what I made]' They are too busy making themselves.

'Do Not Disturb' by Deborah Jackson is published by Bloomsbury on 6 May ( pounds 10.99).