Now that educationalists are, at last, looking at the problem of "within school variation" of attainment by pupils, perhaps it's time to look in depth at what actually happens in schools, rather than what schools say happens, to see why the lowest achievers fare so badly, even in schools that have many pupils who do well in SATS and GCSE exams.
The first port of call in any study must be the general lack of interest in and expectations of the intellectually less able.
This, I suspect, has become more widespread with the introduction of league tables for SATS and GCSE results, which puts emphasis (quite rightly) on how well schools deal with their more able children, but which has, as its corollary, a lack of investment end interest in the children at the other end of the academic spectrum.
All too often, we find that such children are written off before they start as being unprofitable material, allowed to do what they like in class, not expected ever to amount to anything and, as such, are generally given to teachers almost as a punishment.
It is the poor-quality teachers, whom the head doesn't want ruining the chances of the more able who get the lowest sets, along with the inexperienced newcomers, the temporary supply teachers - all of whom have the brief to mind, to try to control and to keep out of sight those pupils who will be excused entry to SATS exams or GCSEs.
Teaching such children anything is often not a priority.
There is, of course, no excuse for this attitude, given that many such classes consist of only a handful of pupils, with all the scope that gives for personal tuition and real progress.
I know of one such class, with only nine pupils where the teacher routinely swore at the children, denigrated and insulted them, and turned a blind eye to the couple sitting at the back of the room canoodling and the girl swigging from a soft drink bottle that actually contained vodka.
Once an inspiring supply teacher took them over, however, the group blossomed and produced work good enough to be put on display on the walls around the school.
Surely, this culture of contempt and neglect has to change if the less able are to make any real progress, along with the mistaken belief that all teachers are equally effective when they teach across the whole age and ability range.
The idea now is that you may be "rewarded" with a few top sets to teach, but you have to take your turn, as some kind of penance, teaching the low sets, the dross.
Teachers should be encouraged to specialise in teaching the lower ability classes, just as teachers should be allowed to specialise in teaching, for example, "A" level.
Some teachers are not up to the job and their students suffer, just as others, given low ability classes in a mistaken attempt at "being fair," are useless at getting the best out of such children.
Let teachers specialise and give the teachers of lower ability sets the same status and pay as the teachers of the most academic and help to bring talented teachers into the job of making children perform to the best of their ability.