They are also expensive for both private and local authority owners to maintain and keep warm in the winter. And so many schools are being turned into large apartments, with the new residents sometimes lucky enough to have the use of the school grounds, if these have not been sold off separately.
"One of the difficulties encountered by developers is how to deal with what is often a very large room with extremely large windows, typical of Victorian schools which have frequently undergone conversion," warns Janice Hennessey of Ekins Surveyors.
"Where these rooms have been carved up, the proportions can appear slightly unnatural. If left alone, they can be dramatic, but the sheer size and height of the room and surface area of window can lead to large heating bills."
Sapcote Real Lofts, which has converted a number of schools in London, has found a way round these problems. It simply divides the schools up into basic shell apartments, supplies the basic services - water, electricity, gas, cable TV and telephone - and then leaves the purchaser to design the interior as he or she would like.
"Sapcote Real Lofts are real because ceiling heights are left untouched. We don't create artificial square footage by imposing galleries where there shouldn't be any, so owners' imaginations can run riot," says the company's chairman, Stuart Sapcote. "What owners buy are the grand Victorian features of these superbly built schools."
Sapcote is currently selling loft apartments at The Paragon in Bermondsey, London SE1, which was opened in 1900. A church-like, triple-volume penthouse loft with exposed timber beams is on the market for pounds 295,000, with the cheapest homes being two semi-detached houses with double volume rooms and exposed beams. These are being sold for pounds 125,000 each.
For the first time, the company has fitted out two of its apartments. These are priced at pounds 199,500 and pounds 170,000. And for owners who prefer using bicycles to cars, taxis or buses, a pool of 15 bikes is being provided.
At the Grade II listed Greenwich Academy, Blackheath Road, south east London, Sapcote has three out of 27 lofts still for sale. This was the West Greenwich Boys School, built in 1874/5 and prices for the remaining lofts range from pounds 165,000 to pounds 187,500.
In Cirencester, Gloucestershire, Redrow Homes is converting Oakley Hall. This was used as a private school for more than 70 years, with pupils including Chris Brasher, founder of the London Marathon, and the broadcaster Julian Pettifer.
The exterior has been restored, together with the 1919 chapel and surrounding Cotswold stone walls, and the old school bell has been placed in the communal lobby. Twelve apartments have been created, of which nine are for sale, priced from pounds 110,000 to pounds 190,000.
A large development in Cheltenham is taking place around the former St Mary's College. The site was bought by TH Kingerlee & Sons, an Oxford- based developer. The first phase is the conversion of a Grade II listed building, now called Shaftesbury Hall, into 31 one, two and three-bedroom apartments. Prices range from pounds 85,000 for a one-bedder up to pounds 150,000 for a three-bedder. There will be 84 homes in all.
In London, the Santley Primary School in Santley Street, SW4 is being turned into 47 apartments with the teacher's block and kitchen block being converted into seven houses by Blenheim Bishop. There will also be 12 new-build three-bedroom houses in the playground.
Trinity House, in Alie Street, London E1, is a 19th-century German Lutheran Church school, which is being converted by Pathfinder into seven apartments and three studios. Its former chapel, with its high ceilings, large arched windows and timber panelling, will become two studios. Prices range from pounds 125,000 for a one-bedroom apartment to pounds 235,000 for the penthouse.
Village schoolhouses also make excellent family houses and Humberts is selling a number of these including The Schoolhouse in Colster- worth, near Grantham, Lincolnshire. This was built in 1893 and converted in the late Seventies into a family home. With five bedrooms, a large kitchen/breakfast room and large garden, the house is on the market for pounds 175,000 through Humberts' Grantham office.
Its Devon office is selling another converted schoolhouse in Luppitt, near Honiton. This was converted 30 years ago into a lovely family home with views over the National Trust landmark of Dumpdon Hill. It has four bedrooms, an office/guest suite on the ground floor and pretty gardens. It is on the market for pounds 265,000.
Sapcote Real Lofts, 0171-937 3878; Redrow Homes (SW), 01285 656006; Pathfinder, 0171-736 9669; FPD Savills, 01865 269010; Blenheim Bishop, 0171-495 1253; Humberts, Grantham, 01476 576133; Humberts, Honiton, 01404 42456