Headteachers fear they will have to sack staff and impose a four-day week in a looming budget crisis.
Brighton and Hove City Council last week received one of the worst government settlements in England for the second year running.
Although headteachers will not know their exact budgets until Christmas there is growing concern they will be facing major financial difficulties, which could lead to staff cuts and even the loss of one day's teaching a week.
Trevor Allen, headteacher at Dorothy Stringer, said: "The definitive figures are not yet available but all indications are it is going to be desperate. It's terrible.
"There is no doubt in my mind it is going to happen.
"I think the Government have really passed the buck to the local education authorities. The Government will say it's far too early because they have given schools four per cent extra and they have given authorities money to support schools. They have but the amount of money is insufficient.
"It is going to leave budgetary problems in a considerable number of schools."
A steering group of headteachers from Brighton and Hove met on Thursday to discuss the crisis.
Last year, headteachers had to dip into reserve funds for things such as building works and some had to set deficit budgets to pay for teaching staff and resources.
Peter Evans, head at Cardinal Newman in Hove and chairman of the city's secondary headteachers forum, has said repeatedly the problems are likely to get much worse as the spending formula means money from the South is redistributed to the North.
Andy Schofield of Varndean School has, in the past, voiced his fears about moving to a four-day week and Liz Fletcher of Patcham High also said there are "real concerns" over budgets.
David Hawker, director of children, families and schools at the council, said: "The settlement is very tight. But it's quite a complicated settlement and we are still working through the implications.
"There will be some money to apply to schools with particular difficulties and that may well resolve the most severe problems."
But Mr Hawker was unable to rule out redundancies and said the schools would only know that once they had the final figures.
He said some schools might find they received more money than expected.
The council had drawn up a redeployment protocol, which it was asking all the city's 76 schools and their governing bodies to sign.
It means if staff need to be made redundant, where possible they would be redeployed in other positions at other schools.
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