The only semi-official definition of a failing school came in last December's ministerial task force report, Improving Achievements in Scottish Schools.
In about 8 per cent of secondary schools, mostly in disadvantaged areas, at least a quarter of pupils did not gain five Standard grades at any level. In some schools, the figure was 40 per cent or more. At least 30 secondary schools are underperforming.
"For these pupils," the report concluded, "the mainstream curriculum is not working." It urged that action plans should be drawn up for such schools.