The Scottish Independent Nurseries Association fears the figures may be used to justify councils cutting back payments for the places they commission from private nursery schools and playgroups.
The research study by Paula Gilder Consulting, funded by the Scottish Office, estimated that educating a child in a private nursery costs pound;537.10 a year, compared with pound;1726.27 in a council-run nursery and pound;868.20 in the voluntary sector.
Patricia McGinty, SINA's vice-convener for strategy, says the accuracy of these figures is open to question. She points out that some private schools refused to disclose staff salaries.
The analysis was based on returns from 207 local authority centres, 87 in the private sector and 48 voluntary groups - 16 per cent of council provision and 13 per cent of the other two sectors.
But the study did not reflect the diversity and complexity of the private sector, Mrs McGinty suggests. Some private schools were in family houses, some in renovated council premises and some in high-amenity areas. Yet property costs were put at just pound;58.30 a year for each nursery child in the private sector, against pound;389.09 for local authorities.
The report did point out that local authority salaries were significantly higher than "apparently equivalent staff" in the other sectors. There was also a huge salary range in the private and voluntary sectors, from pound;3,360 to pound;21,912 a year for managers, compared to a local authority average of pound;27,518.
The researchers do acknowledge there may have been "non-disclosure of some private sector costs". But they say a full picture would only emerge with further research. "Some caution must be used in generalising from the overview of the costs per child".
The conclusions therefore fall some way short of the aim of the study, which was to provide "firm and comprehensive" information on pre-school costs.
The Scottish Office is simply advised: "Whether these (cost) relativities are sufficiently robust to justify a differentiated approach to the Government funding of pre-school education at the present time is open to question."
But SINA is concerned the study figures could be misused by authorities to justify such differentials. Mrs McGinty claims some councils are already commissioning places from the private sector at less than half the pound;1140 per part-time place, which is the basis of the pound;76 million pre-school grant given to the local authorities to replace vouchers.
The Scottish Office guidance on funding says: "Ministers would be surprised if authorities felt they could commission a fully-loaded place, meeting HMI quality standards, for less than pound;850."
But this sum is merely an "advisory floor" and Mrs McGinty claims the authorities are ignoring it, thereby jeopardising quality.
* Renfrewshire Council has hit upon an innovative approach to pre-school partnership. The council is to build a new pound;225,000 nursery school in Kilbarchan and then hand it over to be run by a parent-led nursery.
The move has been made possible by the sale of land on the site of the old primary school in Kilbarchan, which is expected to realise up to pound;700,000. Government rules allow half of the profit in such cases to be reinvested in council services.
The new centre will be run by the Kilbarchan Community Nursery, which currently runs classes for 42 three to five year olds. It employs six staff, of whom one is primary trained. The council will buy 30 part-time places for 60 four year olds under the Government's pre-school funding regime. This will leave the parents to generate additional business from among three year olds and full-time pupils.
Brian Oldrey, Renfrewshire's education convener, says: "Working in partnership is an important issue. Resources are only just becoming available through the Government, and I recognise the contributions the independent sector have made all these years. I have listened to the nursery group and the proposals which have been made demonstrate our commitment to the future."
Sheila Cronin, Renfrewshire's head of community and special services, stressed that the authority would specify the educational standards which the school would have to meet. The nursery has already been registered under the pre-school voucher scheme.
Celia Boyd, president of Kilbarchan Community Nursery, said they were "delighted" with the council's initiative.
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