Chancellor Alistair Darling announced in his Budget speech on Wednesday that schools would receive an above-inflation increase in spending of four per cent during 201011.
But next year is expected to be the last that schools can enjoy the high levels of spending that started back in 200001.
Mr Darling said that public spending will be cut to 0.7 per cent from 1.1 per cent in 201112, which could mean spending on schools will be as low as 2 or 3 per cent once the health service and social security has been taken into account.
Tony Travers, director of the London School of Economics' London Group and expert on the UK economy, gave a stark warning: "What the Government is basically saying is that there will be no change in their spending plan for schools and the health service next year. I would be very surprised if these figures weren't lower in 201112."
By then, according to Mr Travers, when the money filters down to schools, many will be receiving "at best" just 1 or 2 per cent extra per year, and added that he expected Building Schools for the Future money to be dramatically reduced.
"There is no doubting that this is a good year for schools, especially compared to other public services, but it is the last of the good years. My advice would be to enjoy it while you can."
Mr Darling also announced that the Government will plug the hole in sixth-form funding that had left hundreds of schools and colleges scrambling for cash.
Earlier this month the Learning and Skills Council wrote to schools informing them that they would not receive the budgets they had been expecting.
But Mr Darling said Pounds 250 million will be made available this year for sixth-form students, with a further Pounds 400 million for next year, creating an additional 54,000 places for students in the next economic year.
John Dunford, general secretary of the Association of School and College Leaders, said he "strongly welcomed" the move but was concerned over the "1 per cent efficiency saving per student".
"It sounds like giving with one hand and taking away with the other."