With more than 100 permanent teachers on its staff, Langdon comprehensive school in East Ham, east London, uses, on average, a couple of supply staff from a commercial agency each week.
Until recently the school used the supply pool provided by the London borough of Newham, but when it was shut down, Langdon turned to the commercial sector.
Like many schools in London , it finds the agencies can supply subject-trained staff more quickly and easily than the local authority. The school pays about pound;120 for each teacher per day, the same as it paid the town hall.
Phil Wood, Langdon's senior teacher in charge of supply cover, finds it difficult to think of any drawbacks. "The main point of supply cover is to get a suitable teacher straight away in front of the class. The local authority's pool was very limited, but the agency draws from the whole of London.
"It can be a slight problem for staff who are unfamiliar with the area finding us, but we've never had any difficulties with them.
"Very often they are young Australians or Canadians travelling, but they are always very committed and we've never had cause for complaint. On the odd occasion when we have had a query, it has always been sorted out quickly."
At Potters Green primary school in Coventry, the headteacher, Chris Thatcher, appears very happy with the agency staff he uses, on average for two or three days a week.
"From the headteacher's point of view it makes life much easier," he says. "The local authority has a register of supply staff, but you have to ring them individually to find out what they do and if they are available. The agencies do all that for you. And they operate 24 hours a day, so you can ring up at seven in the evening and they will have someone for you the next morning."
Neil Thornley, head of Fearns High School in Bacup, Lancashire, occasionally uses agency staff, but he prefers the school's own list of tried and tested local supply teachers. "Some of the agency people are very good, but we tend to use our own people with whom we've built up strong links, and we also do a lot of our own cover, because we prefer to have people the children know.
"The agencies are also quite expensive when you consider what the teacher is paid at the end of the day. It's a commercial opportunity someone has spotted, and who can blame them for that?"