School leaders have raised concerns that major government exam reforms thave "sounded the death knell" for AS levels which were traditionally popular with many students and universities alike.
This year's results mark a key step in reforms introduced by government - including a move away from coursework and modular exams as well as a significant decision to separate AS-levels to form standalone qualifications.
And this shake-up, which applies to England only, has led to a 42 per cent drop in AS-level entries this year.
A snapshot survey of around 170 heads in England conducted by the Association of School and College Leaders (ASCL) found that around two-thirds (65 per cent) have cut the number of AS courses they offer in the wake of the Government's reforms, while 86 per cent said they expect to remove AS courses in the future.
ASCL general secretary Geoff Barton said: "It is increasingly clear that government reforms have sounded the death knell for AS-levels.
"AS-levels allowed students to study four subjects knowing they would all count towards a qualification, either an AS-level or a full A-level.
"They were intended as a way of broadening the curriculum and were valued by students, employers and universities."
He added: "The great benefit of the old system was that it gave students a broader range of knowledge and allowed them to keep their options open for longer.
"The decision to decouple these qualifications was an entirely unnecessary reform which is narrowing the curriculum and reducing student choice."
Under the previous system, sixth-formers typically took four subjects in their first year of the sixth-form, before deciding which three to continue with to full A-level in their second year.
AS grades were often used by universities in making offers to applicants, as they were an indicator of a student's final A-level results.
The move to decouple AS-levels proved controversial at the time it was announced, with universities - including Cambridge - headteachers and MPs among its critics.
Ministers argued that universities learn little more from knowing teenagers' AS-level results in addition to GCSE grades and insisted that the reform should not affect university admissions.
This year will also see the first A-level grades given in 13 subjects which have been reformed - art and design, biology, business, chemistry, computer science, economics, English language, English language and literature, English literature, history, physics, psychology and sociology.
These changes mean that students sit all exams at the end of the two-year-courses, rather than throughout, with less coursework.