The government wants better deals negotiated on school computers
Schools in England will have to share resources and make smarter purchases to save £750m and safeguard teaching jobs.
Schools Secretary Ed Balls said head teachers needed to start planning now in order to protect frontline services.
And he warned that further steps to ensure schools spend any excessive surpluses they may have accumulated would be considered.
Schools that failed to take a strategic view would find it "challenging" to do well in future, he warned.
Addressing the Specialist Schools and Academies Trust conference in Birmingham, Mr Balls said significant savings could be made by schools working together in federations.
A Department for Children, Schools and Families paper on how schools should safeguard resources said the notion of federations had not been driven by cost savings.
"But reduced costs can accompany improvements in outcomes, and must be welcome in tougher times.
"There is firm evidence that opportunities for greater efficiency exist in federation and we want to ensure that this is maximised," it adds.
The paper gives examples of schools which have saved significant amounts by coming together in partnerships, including three schools which shaved their senior staff budgets in half by federating.
It also suggests "collective bargaining" could lead to significant savings in the procurement of facilities management, energy contracts, the use of supply agencies and photocopier contracts.
Mr Balls said: "Together we have opened up opportunities for thousands more children and young people.
"I am committed to ensuring that this progress continues and that despite tougher times vital frontline services are maintained.
"Now more than ever we need to ensure we are getting real value for money from our investment.
"We will only achieve efficiency savings while at the same time continuing to improve school standards and raising levels of achievement by working together."
Head teachers were also urged to compare their expenditure with that of other schools and examine their staffing plans to see if changes could be made to ensure staff were used effectively.
Mr Balls also announced a £12m initiative to give schools hi-tech "smart meters" to cut their energy bills and reduce their carbon footprint.
The government believe the meters and other energy efficiencies could save primary schools up to £700 a year each and secondaries up to £3,000 a year each on fuel bills alone.
But teaching unions warned the amount that can be saved by efficiencies has been exaggerated and question whether frontline services can protected.
John Dunford, general secretary of the Association of School and College Leaders, said there was no clear evidence that smarter purchasing would save enough to protect services from possible spending cuts in the future.
He added: "For the secretary of state to say that £300million would be saved by federating a third of schools is making the wrong case for federation.
"Decisions to federate should be based on raising standards. Savings cannot be made just through slimming down school leadership structures. Some savings on staffing may be made through re-structuring in the long term."
The National Union of Teachers general secretary Christine Blower said if purchasing was organised at a strategic level through local authorities as it used to be some savings could be possible.
"Asking heads to get together with their colleagues in neighbouring schools to negotiate deals is probably not the best use of headship time."
She added that any energy saving measures should be given serious consideration but that teachers were not a dispensable item."