And because schools lack information, they cannot challenge their bills, say chief education officers.
An analysis of spending in Warwickshire secondary schools unearths a difference per square metre of almost pound;6 in the price of caretaking and pound;2.50 in energy costs.
The authority is now investigating why energy or cleaning prices differ significantly between similar buildings.
The discovery follows a nationwide inquiry by COPROP - the organisation representing chief council officers with overall responsibility for managing property - and CIPFA, the Chartered Institute for Public Finance and Accountancy.
Their report compared the economic performance of local authority offices and secondary schools. And its findings will be useful to headteachers, charged with the difficult task of making the best use of hard-stretched resources.
The report highlights the tendency for less obvious costs such as water rates and insurance to be higher in one school than in another for no apparent reason.
One authority in the South-west, for example, was paying pound;160,000 more than it needed on insurance because it had terrorism cover on all its buildings.
Across the country, water and sewerage rates varied by up to 500 per cent. One school was spending 107 per cent above average - the highest in the survey.
Costs were done on both a per square metre and per pupil basis, and included planned maintenance such as re-roofing.
The school with the highest expenditure levels was spending 29 per cent above the average on energy, 39 per cent more on caretaking and 31 per cent extra on rates.
Peter Ridley, former president of COPROP and Warwickshire's property services director, said heads needed more information.
The research has led to a benchmarking service, meant not to embarrass authorities or schools with high costs, but to secure best value and practice.