Ealing council has passed the administration of its in-house teacher supply list to one of the country's biggest supply agencies.
In return Teaching Personnel is acting as a central clearing house that, it is hoped, will eventually offer schools a choice of all supply teachers in the borough at lower rates via one telephone number.
The company believes that schools will increasingly turn to the council-backed system rather than using the many other private agencies operating in Ealing.
It says this saves on marketing, recruitment and sales costs, allowing it to cut the daily surcharge to schools for every teacher it sends out, from pound;50 to pound;18.
Under the system teachers on the council list continue to be paid according to government pay scales at an average pound;154 a day while those on Teaching Personnel's books are still paid an average pound;110 a day.
Bob Anderson, Ealing council's head of school effectiveness, said: "This is a pilot and we will give it a year but if the feedback we get from schools isn't good enough then we will think again."
Teaching Personnel says that more than three-quarters of Ealing schools have used the system since it was introduced in September. It expects half of all supply business in the borough will go through it by the end of term.