They know that if schools are losing a high proportion of well-motivated pupils from relatively prosperous and educated families, the effect which research has shown such pupils have on the overall achievement by pupils from less favoured circumstances is being lost.

The statistics gleaned from the Scottish School Leavers Survey come as a surprise. Indeed, headteachers from some education authority secondaries do not see any evidence of the phenomenon affecting their school. It has long been clear that academically inclined secondaries attract pupils under the parents’ charter, and several of these fall outside the boundaries of the new Glasgow. But the parallel drift to independent education is unexpected.

The city returns no Tory MPs and only a handful of councillors. It has a long tradition of support for public services that goes far beyond the substantial proportion of its population who would still describe themselves as socialist. But educational aspirations and a readiness to spend money to attain academic success are not confined to adherents of the right, as New Labour is keen to exploit even at the expense of offending traditionalists.

Leaving aside the morality of the assisted places scheme and its use of public money, there must be freedom for parents to choose. But Glasgow councillors will want to ask why so many of those with the means to make such a choice are deserting local authority schools.

Ideally, there should be a social mix in school rolls. Past housing policy makes that impossible in some areas. Evidently there are other factors militating against diversity that merit investigation.