All primary schools should consider "setting" children as it can be a powerful way of improving performance, according to the Office for Standards in Education.
The popularity of setting - grouping children according to their ability in a given subject - is soaring. The number of such lessons doubled last year, according to OFSTED's new report, Setting in Primary Schools.
Last year, 4 per cent of the 400,000 lessons observed by OFSTED were setted compared to just 2 per cent the previous year.
One in four of schools not currently using setting told researchers they planned to introduce it soon.
Setting was much more common in deprived urban areas where there were concerns about low standards. It is not to be confused with streaming where pupils of similar ability are taught together for all subjects. Streaming is rare in primaries, says OFSTED.
Very few schools said they avoided setting because of ideological objections; most cited practical concerns including the small size of the school, uneven composition of year groups or the lack of space or staff. Most schools which introduced setting believed it was the most effective way of matching teaching and resources to pupil ability in certain subjects.
However, OFSTED found that setting polarised the quality of teaching. Frequently teaching was either very good or poor depending on whether staff had modified strategies to cope with setting.
The report said: "Setting by attainment allows teachers to teach the entire group together for a much greater proportion, if not for all, of the time allocated. That important potential advantage can be lost, however, if the teacher continues to teach the set as if it were a mixed-ability class and over-use individual work or further sub-divide the set into ability groups which simply recycle the organisational problems of teaching mixed-ability classes."