COMPREHENSIVES appear to be better than selective schools at reducing the achievement gap between social classes, according to research published next week.
Detailed analysis from an international survey shows that education systems which separate pupils at early ages show a stronger link between social class and academic achievement.
Countries which send pupils through different types of programmes within a school, or send them to different types of school, also tend to produce lower reading performances, researchers say.
Educationists warn care must be taken when changing the British comprehensive system to make sure that increased specialisation does not have the same effect.
The research was conducted by the Organisation for Economic Co-operation and Development through its PISA survey of student skills and knowledge in 30 countries.
An OECD spokesman said: "School systems that differentiate between pupils through institutionalised streaming at early ages tend to produce lower reading performances while failing to moderate the impact of social background on student attainment."
The Government's plans for secondary education include increasing the number of specialist schools.
International education consultant Donald Hirsch said: "What we mean by specialisation doesn't necessarily lead to institutionalised streaming, but many people fear that it could lead in that direction.
"It needs to be recognised that our comprehensive system in its present form has had some apparent advantages over systems which have separated students.
"Therefore any measures which do separate students need to be considered very carefully to ensure that all students, regardless of background, have the best possible opportunities."
A publication containing the new findings, entitled "Reading for Change", will be published by the OECD on Tuesday.