By BBC education correspondent Mike Baker

Selection - or at least partial selection - is back on the agenda again after the well-publicised comment from the prime minister's official spokesman that the days of the "bog standard comprehensive" are over.

But are comprehensives in England "bog standard"? Is it still right to equate comprehensive education and mixed ability teaching?

It is certainly true that the practice of teaching children of all abilities together began to spread as the comprehensive school movement gained momentum from the mid-1960s.

However it took a long time to push out the more traditional approaches. There were three of these:

• Banding involved putting pupils into broad ability bands and was often used to ensure each school in an area had pupils representing a reasonable balance of each ability level.
• Streaming meant splitting pupils into several different hierarchical groups which would stay together for all lessons.
• Setting meant putting pupils of similar ability together just for certain lessons. So, for example, it would be possible to be in a top set for French and a lower set for mathematics.

As late as 1970, 70% of secondary schools were still using some form of banding, streaming or setting for first year pupils.

But mixed ability teaching was already becoming more popular with teachers. The Plowden Report of 1967, which cast doubt on the accuracy of selection at age 11, had encouraged this trend.

By the mid-1970s, a study by schools inspectors found that 35% of schools used mixed ability teaching "in most subjects" in the first year. Of course, mixed ability teaching levels are more likely to be highest in the first year, which many secondary schools regard as a transition phase from pupils coming up from primary schools.

By the early 1990s, a survey by authors of a study of comprehensive schools (Benn and Chitty) found that just over half of all schools were using mixed ability groups in all subjects in the first year. A further quarter used mixed ability combined with setting in no more than two subjects.

Hard to do

However, by this time the tide was turning and many leading educators were questioning the effectiveness of mixed ability teaching.

In the early 1990s, Professor Eric Bolton, the former senior chief inspector of schools in England, said few teachers could do it effectively.

He believed that "most teachers aim for the middle: The bright children are frustrated and the ones at the bottom get left behind".

The latest picture is given by this year's annual report of the chief inspector of schools which says "almost all" secondary schools set or band pupils by ability.

The extent of setting varies greatly from subject to subject. Three-quarters of maths lessons observed by inspectors used ability sets and it was used in well over half of all lessons in science and foreign languages.

After that, setting falls away sharply for other subjects - for example English (42%), geography (31%) and information technology (19%). Very few PE, art or music lessons involved setting.

Anyone seeking definitive advice on which method is best will, I fear, be disappointed by the chief inspector's conclusion that "there is no clear statistical link between the extent of setting in schools and the attainment of pupils".