The BBC's Robert Hall reports on the growing popularity of summer schools.

The National Association of Playing Fields has launched a campaign to promote awareness of the importance of play.

And it has written to the Education Secretary, David Blunkett, to ask for help to prevent children growing up into a generation of "nerds, robots and anoraks".

The organisation says after-school clubs put too much focus on adults telling children what to do.

'Filling bottles with learning'

It also believes that homework clubs and holiday learning schemes are robbing children of their free time.

This year there will be half a million pupils taking part in summer schools and sports centres, designed to help young people catch up with lessons or to develop skills in sports or outdoor activities.

An additional 25 summer schools opened last month, part of a growing trend to use the break to help children who have struggled to keep up with lessons during term time.

Summer schools have been encouraged by the government as a way of helping children to bridge the gap between primary and secondary schools, making sure that children do not begin their new schools already at a disadvantage.

But the director of the playing fields association, Elsa Davies said: "We need to provide the right environment in which youngsters can organise their own play.

Is education taking over children's lives?

"We're not against homework and after-school clubs, but you've got to be careful. Activities for children are structured too much. There's too much emphasis on filling bottles with learning."

Mrs Davies is also critical of the new proposals for the Office for Standards in Education (Ofsted) to inspect pre-school centres.

This will put too much emphasis on formal learning in nursery education, instead of children learning in "the most natural way" through play, she said.

"Education these days seems to be encroaching and encroaching, with homework for young children, and assessment for young children - it's taking over their lives."

Life skills

The association has sent Mr Blunkett copies of its new posters, which carry the messages "No play - No childhood", and "Let them play - Childhood is short enough".

Mrs Davies said: "Children learn through deciding on their own play. They learn about sharing, working as part of a team, and doing their own thing.

"It helps them gain confidence, and learn skills which they will use through life."

Too much emphasis was put on computers, meaning children would grow up to be "nerds" unable to interact with other people, she said.

"One of the leisure activities these days involves children sitting in front of machines, often in their own homes. They've got to play with other boys and girls, and not just sit playing with machines."