But energy saving is not just a question of schools scraping up a little extra cash to replace what the Government has taken away. It can bring substantial dividends and give schools a lot more control over their budgets.

Many energy-saving measures are just good housekeeping, such as shutting doors and windows or turning off lights. Some low-cost improvements can be incorporated in maintenance - fitting draught excluders around doors and windows, spring mechanisms to doors to keep them shut, and replacing ordinary light bulbs with the low-energy variety. For example, Coulsdon Church of England primary school in Croydon swapped all its 65W argon-filled fluorescent tubes for 58W higher-efficiency krypton tubes on a maintenance replacement basis, saving energy at no added installation cost.

Most education authorities employ energy managers in their building services departments. They carry out energy audits which pinpoint how energy is being used and where money can be saved.

Andy Thompson, the head ofOakwood, a mixed 11-16 secondary school in Horley, Surrey, asked for an energy audit when local management was introduced.

Since Mr Thompson started his energy efficiency campaign, the school roll has increased from 770 to 1,320. “I couldn’t do a lot about staff costs, I couldn’t do a lot about capitation - but I could do something about energy bills, ” he says. They are now 20 per cent down on the 1989 figure.”

Some of the savings come from imaginative management and an attention to detail - for example, reorganising the cleaning rota to ensure floors were scrubbed in the evening when they could be left to dry overnight rather than in the morning when windows had to be opened to speed the drying.

Mr Thompson believes in involving the pupils in the campaign. “We have a green team - a rota of six pupils organised through their heads of year - to check that lights are switched off and that doors and windows are closed after school.”

Other savings involved capital outlay on installing controls on heating, lighting and plumbing systems. Helped by his local authority, Mr Thompson introduced motion sensors to control the flushing of boys’ urinals and fitting water dams in cisterns to reduce water using in flushing. The Pounds 1, 800 cost of installation has paid for itself in a year.

And another investment was fitting valves to zone the school’s central heating system into six circuits, giving greater control over heating. “When our adult education classes meet after school it means we don’t have to heat up the whole teaching block of 40 classrooms - only the six that are needed.”

The London Borough of Croydon meets three-quarters of the cost of these capital projects. Schools must find the rest of the money, but benefit directly from the savings. Phil Sivell, the borough energy manager, says: “This gives schools an incentive to ensure that any equipment put in is used to its maximum efficiency.”

Capital projects do not have to be large or complex to save money. Dorset energy manager Jim Rutter is currently remetering the oversized water meters that were fitted in schools in the Sixties and Seventies. “For a cost of Pounds 300 we can save Pounds 3,000 immediately.”

The old meters were more suited to industrial users, and the privatised water companies have been charging schools industrial rates for water they were not using. “We’ve had schools with 4-inch mains and 4-inch meters which we have replaced with 1-inch meters,” explains Mr Rutter. “The smaller meter still gives a flow of 1,000 gallons an hour which is more than adequate and we can trickle-feed storage tanks overnight if need be.”

Even changing energy sources can produce dramatic savings. Mr Rutter cites an example of a school which had to scrap a relatively new heating system. He explains: “It was paying peak prices for its electric radiant heating. Simply switching to gas has reduced this bill by three-quarters.”

The school’s new gas radiant heating is an on-demand system that is ideal for large halls which are not in constant use. Heat is reflected downwards so is not wasted. Mr Rutter says: “You don’t heat the room up. You just heat up the people in it.”

Dorset is introducing a building energy management system (BEMS) and has installed computer controls in nearly half of its 350-plus schools. These provide performance print-outs, enabling the system to be fine-tuned for maximum efficiency.

There are additional savings from reduced maintenance costs and more efficent fault diagnosis. BEMS computers also provide fault diagnosis and are linked by telephone line to a central computer at the county’s energy management office. If a boiler or a pump fails, an alarm is triggered on the central computer and engineers can see which part has failed, which means they can send out a properly equipped repair team.

Lighting control systems which work on demand are also popular. Passive infra-red (PIR) or microwave sensors switch lights on in sports halls or corridors when they detect movement. Surrey has fitted PIR systems in 60 schools. Far more sophisticated is daylight-linked lighting using a ceiling-mounted photo cell to control ambient lighting levels and turn up lights if level falls below a pre-set level. The cost of fitting a new daylight-linked lighting system for a big secondary school is Pounds 20,000-30,000. It is far more cost-effective to incorporate the sensors as part of an energy saving design for a new building.

One of the biggest areas of energy loss is the school swimming pool. Dave Hampton of the Building Research Energy Conservation Support Unit, a Government-funded research and information body, says: “Energy use is crucial in schools which have swimming pools. A typical 600-pupil school with a heated pool may have an energy bill of Pounds 30,000, of which a quarter or more is spent on heating the pool.”

The high energy consumption is the result of having to keep the hall ventilated to reduce air humidity. Minimising water evaporation reduces the need for ventilation and heat loss. Ideally, the air temperature in the hall should be one degree Centigrade higher than the water in the pool, which in turn should be no warmer than is absolutely necessary. The pool should be covered when not in use.

Mr Hampton believes the lessons to be learned from saving energy in schools are essential if attitudes towards the environment are to change.

“Schools have a key role to play in understanding energy efficiency and increasing awareness of the concept of sustainability.

“There is a popular saying that we don’t inherit the earth from our forefathers - we borrow it from our children.”