The Inspectorate sets out a 13-point warning note on school costs, making the information the most cautionary of all the school tables issued by the Scottish Office.
The audit unit, which produces the data, is anxious to ensure the public is not misled into thinking costly schools mean generous provision, and cheapness reflects cost-effectiveness. The Scottish Office points out that councils have "flexibility" in compiling their figures.
The tables, which cover 1995-97, again confirm that unit costs are lowest in the high-occupancy schools of East Renfrewshire. Schools there cost pound;2,462 per secondary pupil and pound;1,445 for each primary child. The most expensive are in sparsely populated Shetland, at pound;4,793 a head in secondaries and pound;3,214 for a primary place.
These costs put East Renfrewshire primaries pound;350 below the national average of pound;1,795, while Shetland is almost double the Scottish figure. East Renfrewshire's secondary costs are pound;325 per pupil lower than the national average of pound;2,787, which Shetland exceeds by pound;2,006.
The continuing message is that rural education and smaller schools cost more: a secondary with a roll of 300 would expect to have running costs per pupil around 50 per cent higher than that of a school with 800 pupils. Holyrood Secondary in Glasgow, with 2,077 pupils in September 1996, is still among the cheapest to run, at pound;2,313 per pupil. But the title for the most efficient secondary is now held by Williamwood High in East Renfrewshire, whose 1,307 pupils cost pound;2,251 each.
The most expensive secondary by far is North Walls junior high, a two-year school on the island of Hoy off Orkney where the 10 pupils cost pound;15,960 each. The only other authority now left with two-year secondaries is the Western Isles, where the costliest provision is at Daliburgh School in South Uist. With only three pupils more than North Walls, it is almost pound;7,000 per pupil less expensive.
The largest primary is Carolside in East Renfrewshire, although a bill of pound;1,265 for each of its 774 pupils is not the cheapest in the sector. That distinction belongs to Lilliesleaf in the Scottish Borders where the 98 pupils cost a remarkable pound;1,215 a head. This represents a decrease of pound;300 over the three years, although the roll went up by only 15.
John Taylor, assistant director of education in Scottish Borders, said the main factor was that Lilliesleaf was at the limit of the staffing formula which has now been increased from a teaching complement of 4.2 to 5.2 because of the rising roll. The school has a younger than average staff, which also reduces costs.
The most expensive primary is Kensaleyre on Skye where the five pupils cost pound;12,197, more than six times the Highland primary average. This may not last much longer, however, since the school is on Highland's closure list. It now has seven pupils but a capacity for 47.
The figures in the tables do not necessarily reflect the actual costs of educating pupils in each school, since the provision of debt repayments or special educational needs may be defined as central education authority costs in some areas and not therefore allocated to schools. Running costs may also be affected by differing sums being delegated under devolved management.
School-based costs of primary education have risen over the three years by 4.75 per cent to pound;793 million. There has been a 3 per cent increase in secondary costs to pound;882 million. These represent real terms increases of 2.6 per cent and 1.4 per cent allowing for inflation.