The schools have been taking part in a ground-breaking programme in which they have managed to cut their energy use by up to 40 per cent through making a series of simple lifestyle changes.

They have dramatically reduced their carbon footprint by switching off computers and lights, filling kettles with only the amount of water actually needed, turning down thermostats by one degree and keeping windows draught-free.

Now the programme, developed and run by the National Trust in partnership with Norfolk County Council, is bringing together about 140 schoolchildren at Swaffham's environmental showpiece on Thursday, from 1pm to 5pm.

The pupils will be going head-to-head in a three-category competition to take their energy-reducing work even further – by going out to businesses, taking their messages home and inspiring other community groups to cut their energy use.

Results and winners will be announced at the event, where there will be guest speakers and prizes for all the children involved.

Norfolk County Council has helped fund the Energy Busters programme for the past four years and even more schools will be involved this year.

Rosalie Monbiot, cabinet member for children's services, said: "It is crucial that our schools become more energy efficient as they consume three-quarters of the energy used by Norfolk County Council.

"Teaching children about the importance of saving energy is vital if we are to cut our carbon emissions as they can continue these good habits throughout their lives.

"This project has given children a real chance to nurture their enthusiasm for protecting the planet. The programme has also given them valuable lessons to take home to friends and family."