Setting by ability appears to be back in official favour again. In the drive to raise standards, schools are being encouraged to adopt this tactic by both the Government and the Office for Standards in Education.

Some secondary schools are already grouping pupils on the basis of assessments at the end of primary school. But is ability grouping really the key to raising standards for all?

The type of grouping favoured by the Government is setting, which means that pupils are grouped according to their attainments in each subject, so a pupil may be in a high set for one subject, and a lower one for another.

At present, a minority of schools teach pupils in mixed-ability classes for all subjects up to age 14, but most use sets for at least one or two subjects. Very few schools use streaming, in which pupils are grouped into classes according to their general ability and then have all their lessons with that class.

Streaming was common in the 1960s, but its popularity decreased when it was found to alienate young people in the lowest groups. There is now some anxiety that if setting is adopted in all subjects, some pupils will be in the top sets for all subjects and others will be in the bottom sets - a situation that may bring back the same problems as streaming.

Low-ability groups tend to include disproportionate numbers of pupils of low socio-economic status, ethnic minorities, boys and those born in the summer. Once placed in a low group, the possibility of moving into a higher group is limited and pupil motivation may be adversely affected.

There is little hard evidence available about the effects of formalised grouping practices on academic achievement in this country since the introduction of the national curriculum. Research from other countries - and predating the national curriculum in this country - shows that there are advantages and disadvantages to formalised grouping.

The picture is complex and pupil grouping is only one of several factors affecting learning in the classroom. International reviews indicate that when pupils are randomly allocated to either ability groups or mixed-ability groups there is little or no difference in average attainment. Also, that differential effects of pupil-grouping procedures on achievement depend mainly on the course content. Where the course content for the year is fixed, ability grouping makes little difference to attainment, but systems with the greatest adjustment of content produce the largest differential effects on student learning.

These systems allow higher groups to move on and take different courses, leaving those in the lower groups even further behind with little chance of ever catching up. Simplistic comparisons with other countries can be problematic, however, as so many other cultural factors need to be taken into account.

A research team at the Institute of Education, University of London, is currently investigating the effects of different types of grouping on pupils in the lower secondary school. The research, which is funded by the Economic and Social Research Council, will obtain information on pupils’ academic achievement and also on non-academic outcomes - including attitudes towards school, attendance and rates of exclusion.

The project will provide information about schools’ procedures for allocating pupils to groups and about teachers’ attitudes towards ability grouping. It aims to provide information that will help schools to make decisions about grouping.

Through our contacts with schools, we are beginning to hear about alternative approaches such as cross-age grouping, modularising the curriculum, developing individual learning plans, or deploying staff in ways that maximise the flexibility of learning groups. We would be interested to hear from other schools that have adopted innovative approaches.

Given the implications of ability grouping for the education and future employment of young people, there is remarkably little research to enable schools to make informed choices. We hope that our study will make clear the advantages and disadvantages of ability grouping and help schools to meet the challenge of raising standards for all.

Dr Judy Ireson is co-director, with Dr Sue Hallam, of the Ability Grouping in Schools Project. It is based in the Psychology and Special Needs Group, Institute of Education, University of London.