Government attempts to get students to study a broader range of subjects in the sixth form have had mixed success, new research suggests.
Since AS-levels were introduced in 2000 the numbers of students taking the broadest combination of an exam from each of the three main subject areas - science, arts and humanities - doubled.
But the new analysis of exam entries shows this broadening appears to have been confined to the lower sixth year, and the AS-level in particular. At full A-level, the numbers taking a narrow range of subjects has actually increased.
The findings, based on exam entry figures for 20012, will raise the pressure on the Government task force which is proposing a baccalaureate-style diploma for a more rounded education.
In 2001, the last year of traditional A-levels, one in 10 sixth-formers chose a combination of sciences, arts and humanities. In 2002 a fifth of candidates took an A-level or AS-level in all three subject areas.
But when the researchers at the University of Cambridge Local Examinations Syndicate, looked at the figures for the full A-level alone, the numbers sitting exams from all three areas fell, from 10 to 9 per cent.
Those taking all their A-levels from just one of the three areas rose, from 30 to 35 per cent.
John Bell, who led the research, said that some students were now taking an extra AS-level outside their "specialist" area in the lower sixth, but then playing to their specialist strengths at A-level.
The Curriculum 2000 reforms have been plagued by problems. Critics say they were rushed, giving schools huge headaches when the AS was first taken in 2001 and contributing to last year's A-level regrading controversy.
But John Dunford, general secretary of the Secondary Heads Association, said: "There has been an underlying assumption that Curriculum 2000 did not broaden pupils' studies. These figures suggest that was not the case.
People are studying more widely for an extra year, then re-thinking their options at 17."
The research, which analysed subject choice by students' prior GCSE results, confirmed that higher-attaining students tend to favour traditional subjects such as maths, science and languages. Subjects such as business studies and media studies attracted sixth- formers with lower results at GCSE.
It also uncovered a staggering 21,000 different A-level subject combinations among the 200,000 candidates entered in 2002.