It is easy to forget how common streaming was in the days when the 11-plus still loomed over the upper junior years - or was, at best, a recent memory.

Of the schools that were large enough to stream, 65 per cent were found to be unequivocally doing so, while only 11 per cent were committed to mixed ability. The rest streamed some of their children some of the time.

A study of teachers’ attitudes revealed that most approved of streaming and most favoured the approach of the schools in which they found themselves teaching.

This is a significant finding because the attitude study also revealed that the decision to stream or not reflected a distinct difference in educational philosophy among teachers at a time when the divide between progressives and traditionalists was not widely discussed in public.

In streamed schools, teachers appeared to be more systematic in their approach and gave more attention to the basic skills. The staff were slightly older and more experienced and approved of A- stream children and the 11-plus. Unstreamed schools were more “permissive” about behaviour, and placed more emphasis on self-expression, learning by discovery and practical experience. Teachers in unstreamed schools were more likely to disapprove of the 11-plus.

In a straight comparison of children, using tests in reading, English comprehension, problem-solving and mechanical arithmetic, pupils in streamed schools attained a slightly higher mean score than those in unstreamed schools. There was least difference in reading scores and most difference in mechanical arithmetic, which reflected, the researchers thought, the different emphasis in teaching.

When they looked in more detail at the way teachers taught, it turned out that staff who believed in streaming were using more “traditional” lessons even when they worked in unstreamed schools, and were gaining better results, particularly in mechanical arithmetic and English comprehension. But the researchers warned that the differences were small and that the tests were inevitably biased towards more traditional approaches.

Meanwhile, classes with pro-streaming teachers produced higher levels of anxiety about tests among some girls, and higher numbers of boys who appeared isolated. Streaming teachers found fewer of their male pupils “a pleasure to have in class”. It was not clear whether greater anxiety actually helped girls perform better or inhibited their performance.

The Plowden research lent some credence to the common objection that streaming is inflexible and relies on assessments of potential that are unfair. One of the studies showed clearly that the lowest streams contained more children who were young for their age group and had been in school for a shorter period.

A-streams were dominated by the oldest children in the year group. Two-fifths of children allocated to remedial classes had only six terms of infants-school experience, while only 12 per cent had been in infants school for the full nine terms. This trend appeared among the youngest junior-school children and persisted right through to the top juniors, reflecting the low rate of transfer between streams that was also commonly found. The length of time a child spent in infants school was evidently having an effect on a child’s school career, and the chance of a grammar school place, right up to the age of 11.

The researchers suggested that if all children started school at the beginning of the school year, some of the disadvantages of being the youngest might be ameliorated.

The A-streams also attracted the most experienced and consequently older teachers - those most strongly in favour of streaming and 11-plus selection. On the whole, they were less “permissive” about things such as noise in the classroom and were more likely to approve of their A-stream children.

Lower-stream classes tended to be smaller and therefore benefited from more generous classroom space. But in schools where there were differences in classroom accommodation, the lower streams were generally allocated the darkest, north-facing rooms.

Parents, who were also surveyed, generally supported streaming for their sons and daughters. Of those who had a preference for a type of secondary school, the majority wanted their children to go to a grammar school. This was at a time when the option of a comprehensive school for the children studied was still quite rare.

WHAT THE TEACHERS TOLD PLOWDEN

The committee conducted a general survey of a random 3,000 teachers * 58% of the primary staff believed that all children should enter school at the beginning of the school year.

* 72% believed that nursery education should be available for all children whose parents wanted it.

* 51% believed that children should be able to start school on a part-time basis.

* Most gave priority to group teaching, followed by iindividual work, with class instruction last.

* Three-quarters believed satisfactory standards were being reached with children of average ability, but only half believed this was true of children of exceptional ability and more than half believed low ability children were under-achieving.

* 88% believed corporal punishment was acceptable but only as a last resort. Only 5.8% thought it should be forbidden.

* Between 80% and90% of all teachers made training in basic skills their top priority, in preference to factual instruction and creative work.

* 57% of the sample believed in comprehensive secondary education, 32% were against and 11% undecided.