Since 1994, however, all GM secondaries in the south London borough have been subject to the common funding formula and governors at Charles Darwin cannot wait to see the back of it.
According to chair of governors, Mervin Sharp, the CFF has led to greater confusion over how the school's budget is calculated, with Bromley and the Funding Agency for Schools frequently locked into disputes over figures provided by the council, including a wrangle over pupil projections which was decided in the courts.
Headteacher Rob Higgins agrees. "The formula has never been the same two years running. It was supposed to make things transparent but in reality it's still semi-opaque."
The CFF is calculated by taking Bromley's standard spending assessment for schools, which is just under Pounds 100 million, and subtracting the percentage the LEA may retain for spending on all schools for such things as statemented children and transport. Since 1994, this "top-slice" has increased from about 13 per cent to 18.8 per cent so that, in 1996-97, just over Pounds 80 million was left for schools within and outside local authority control.
The primary:secondary split in Bromley is about 45:55 and this year 17 secondary schools (all but one of which are GM) are entitled to a total of Pounds 44.3 million. Charles Darwin receives just over Pounds 2.5 million, based on four core factors - age-weighted pupil units, special needs pupils without statements, free school meals and fixed costs.
"It's a complex method and the top slice is difficult to understand," says Mr Sharp. "There is no way that the school can realistically check whether it's fair. "
According to Mr Sharp, the CFF is not common but unique to each LEA. In recent years, Bromley has adjusted its age-weighted pupil units so the primary sector is better off at the expense of secondary schools.
Mr Higgins explains: "Because it had encouraged secondaries to opt out, Bromley was in a position to change the AWPUs and increase funding to primary schools which remain under the LEA."
Mr Sharp hopes a national formula will allow the school to plan ahead by giving it more insight into how much money it will receive from one year to the next.
"But the problem with any formula is that there is no mechanism to reflect a particular school's problems. I wonder if there needs to be a better bidding system for the different pots of money."
Mr Higgins, meanwhile, can see political repercussions for the Government if GM budgets no longer reflect spending within a local authority. "At present the Government and local authorities can play one another off over who is really responsible," he says. "If we went for a NFF and schools were funded directly, we would know whose door to knock on when they were complaints of under-funding."