Parents who understand the complicated admission arrangements of schools in inner London are more likely than the less well-informed to get a place for their child at the school of their choice.
According to the Centre for Educational Research, parents now have to deal with a fragmented system, and may have to make multiple applications to several local education authorities.
The change has come about because more schools, mainly grant-maintained and city technology colleges, are responsible for their own admissions.
The research, by Hazel Pennell and Anne West, suggests that parents of pupils who are less able have less choice because schools are operating their own banding system or introducing partial selection. There are also fears that schools may be using interviews as part of covert selection.
Most London boroughs have abandoned the banding system developed by the former Inner London Education Authority to obtain a balanced intake in schools. Those that have kept banding are Greenwich, Hackney, Lewisham and Tower Hamlets, though the latter two have gone from three bands to four.
A number of church and grant-maintained schools have introduced their own banding system. Some schools have attempted to maintain the same balance of ability as obtained by the ILEA formula (25 per cent most able; 50 per cent average and 25 per below average). Others have changed the formula to obtain a more academically able intake (40 per cent most able, 40 per cent average and 20 per cent below average).
According to Ms Pennell, the new grant-maintained schools have begun to interview. In London, a large proportion of the 21 grant-maintained schools are former Catholic voluntary aided schools with a tradition of interviewing parents.
"It is difficult to be certain about whether there is an increase in interviewing, but it is likely that the more schools are given power to select their intake, the more likely there is to be covert selection," she says.
Changing Schools: Secondary schools' admission policies in inner London in 1995 by Hazel Pennell and Anne West is available from the Centre for Educational Research at the London School of Economics and Political Science, Houghton Street, London WC2A 2AE. Price Pounds 5.