Pupils at academically successful schools are more likely to specialise in maths and science at A-level, a study by the National Foundation for Educational Research has found.
By contrast, take-up of these subjects in comparison with other A-levels is particularly low in schools where a high proportion of pupils receive free school meals.
The findings, published this week by the School Curriculum and Assessment Authority, follow concern at the decline in the number of post-16 students specialising in maths, physics, chemistry and biology.
Two-thirds of students taking maths and science at A-level now combine the subjects with arts courses, prompting fears of a shortage of young people qualified to study maths, science and engineering in higher education.
However, while the researchers identified various correlations between A-level choices and school type, location, GCSE results and whether it was co-educational, they concluded that "there are no easy solutions to the challenge of encouraging more students to take mathematics and science A-levels".
They added: "It is not simply a question of devoting more time to the teaching of maths and science pre-16, choosing modular A-level courses or recruiting more suitably qualified teachers."
A questionnaire of teachers at 722 schools and 136 colleges in England and Wales found that the primary reason for the lack of interest in maths and science was the subjects' perceived difficulty at A-level.
This was partly linked to gaps in the syllabus between GCSE and A-level. Maths students, for example, began their A-levels with insufficient knowledge of algebra. The double-award GCSE was seen as an inadequate preparation, particularly for biology and chemistry A-levels.