Of all the justifications advanced for setting, the appeal to common sense is perhaps the most insidious. It suggests that some children simply have more ability, or intelligence, than others; that it is more or less fixed and measurable by tests; and that we can predict with some certainty how they will learn as a result.
This is the common sense view of the world. But as professionals, we surely have to examine such views and challenge them when we have evidence to do so.
We have challenged, in my professional lifetime, such common sense views on gender, race and social class, though in some of these cases the struggle still goes on. Common sense can spawn very persistent myths.
Of course, the setting debate is not new. In the 1960s, opposition to the selection of pupils based on ability was so widespread among professionals and politicians of all parties that comprehensive education and the concept of mixed-ability teaching were introduced in order to ensure that no child had limits placed on their potential to learn successfully. My first appointment was in a junior secondary where I saw at first hand the consequences of selection by ability. By the time pupils had been placed in 3m2 (boys), they had got the message that they were "thick".
So why, after four decades of comprehensive education, during which time Scottish teachers have become familiar with theories of intelligence that challenge the notion that some children are thick, are we still having this debate? We can safely assume that no headteacher or head of department would introduce setting deliberately to harm pupils.
Presumably, the motivation for this practice stems from this common sense belief that some pupils are more able and others less able, and that these two groups cannot learn together.
In Brian Toner's school, parents were consulted and were underwhelmed by professional concerns about setting. Of course, most of these parents will have themselves been through a Scottish education system which has always seen setting as its default position. And, as we know, they have a tendency to leave such professional decisions to us, the teachers.
But surely we have a duty to engage with them in an informed discussion based on evidence? Philosophical, sociological and political perspectives are not, as Brian suggests, irrelevant, nor are they beyond the grasp of parents.
The group that rarely gets consulted is the pupils themselves. Dylan Wiliam and colleagues from Kings College in London did just this in the late 1990s and found that pupils in top maths sets reported that they felt stressed, that they enjoyed the subject less because of the heavy emphasis on exam-based work and often felt guilty that friends had not got into the top set when they felt the were equally able at maths. More recently, Chris Smith and Margaret Sutherland at Glasgow have reported concerns among young people about the practice of setting.
When Tell them from me was written in 1980 by Gow and McPherson, it reminded us that the pupil voice needs to be heard when we as professionals make decisions which might affect their life chances.
Perhaps the strongest argument against setting nowadays is that it is irrelevant. Formative assessment and learning and teaching approaches that stress co-operation, creativity and pupil understanding should make setting a thing of the past. If schools can reduce class sizes, as many are doing, and if they can occasionally free an extra member of staff, as Brian did in his school, why create "less able" and "more able" classes when we know that pupils learning together and teaching one another helps all learners?
The suggestion that if we take the longer view of young people's lives then professional concerns about such matters as setting fade into insignificance needs to be challenged too. How many people are there still around in their 50s or older who are still living with the consequences of having been directed to a junior secondary school or having been allocated to the bottom stream or set?
The irony is that we know that setting exacerbates problems that should concern us. Bottom sets often have disproportionate numbers of (young) working-class boys and young people from minority ethnic backgrounds The recent book Learning without limits (Hart et al, 2004) provides not just a comprehensive review of the ways in which views of intelligence have limited our expectations of young people's capability to learn. It also gives compelling case studies of teachers in every sector who choose to teach pupils in mixed-ability classes and who so do with creativity, with commitment and with success.
Setting versus mixed-ability should be yesterday's debate. Tomorrow's debate is about freeing teachers and others to work with young people in creative and innovative ways so that they can develop as successful learners, confident individuals, effective contributors and responsible citizens.
The way forward may be to focus on the learning process and the factors that promote and hinder it. We need to continue to look critically at ideas and approaches to learning and teaching that render setting obsolete.
Already, schools and local authorities are doing just that, whether it is co-operative learning, thinking skills or dialogic teaching.
Too many young people underachieve, particularly in areas of social disadvantage, but it is not, as common sense might suggest, because they are "less able" than their contemporaries. Setting does not promote successful learning; good teaching does.
Brian Boyd is professor of education at Strathclyde University.