State schools are to be warned that they are not allowed to use interviews to cream off the brightest children.

Ministers are to re-issue guidelines on schools' admissions later this year to remind schools they cannot select pupils.

It follows two rulings against popular comprehensives over their use of interviews.

The most recent case is that of Prendergast School in Brockley, Lewisham, in south east London.

Social selection or otherwise is not part of our strategy for raising standards Department for Education

The local government watchdog, or ombudsman, ruled that the local council was guilty of maladministration because the school used interviews to select pupils.

Government rules mean that state schools cannot select pupils on ability.

Their admissions are meant to be governed by criteria such as where pupils live and whether they have siblings at the school.

Faith schools are allowed to interview families to check their commitment to the school's religion.

Prendergast School was criticised for asking prospective pupils about their interests and what books they liked to read.

Over-subscribed

The ombudsman said three girls who were turned down for places after interviews should be allowed to re-apply.

He also said the local council should pay �250 to each of the girls' families as compensation.

In its defence the school said it was heavily over-subscribed, with 551 applicants for 95 places.

It says it has "noted" the ombudsman's comments and interviews will no longer be used for admissions.

Social selection

The guidelines on admissions will be republished once the Education Bill which is going through parliament has become law.

A spokesman for the Department for Education and Skills said schools would be reminded they were not allowed to select by academic ability or social background.

"We have made it quite clear that social selection or otherwise is not part of our strategy for raising standards," he said.

The other case to hit the headlines concerned the school which topped the league tables for GCSEs last year, Coopers' Company and Coburn School, in Upminister, Essex.

As a Christian school, it is allowed to interview pupils but the ombudsman said it went too far in asking pupils questions that were not about religion.

There is a grey area about interviews and selection in that state schools are allowed to meet the families of prospective pupils for an informal "exchange of information".

Critics argue these meetings can be used to sift out children from middle class backgrounds who might keep the schools at the top of league tables.

Specialist schools are allowed to select a proportion (10%) of their students on aptitude in the school's chosen area of specialism.