It said that AS levels offered a “strong measure” of how well students were likely to perform at A level.
From next year, AS and A levels will be treated as separate and distinct qualifications, and A levels will revert to being traditional two-year qualifications with an end-of-course examination. Since 2000, the AS levels have been treated as the first half of an A level, with the grades in both examinations combined to give a final mark.
However, Michael Gove, when education secretary, took the decision to “toughen up” the qualifications by bringing back testing at the end of the two-year course.
Now admissions officers at Cambridge have challenged the decision, claiming AS levels are a “robust indicator of student progress”.
Dr Mike Sewell, director of admissions for the Cambridge colleges, said in a letter to schools and colleges: “We strongly encourage potential applicants to take AS level examinations in at least three, and preferably four, subjects, whether reformed or not, at the end of year 12.
“This will provide us with a strong measure of applicants’ recent academic progress, will assist us and the students in judging whether an application to Cambridge is likely to be competitive, and will provide reassurance that grade predictions are not relied upon too heavily in a new system.
“AS levels taken in four subjects can provide an extremely useful, externally assessed exam that will avoid schools and colleges having to resource and run their own internal mocks.”
The letter added that AS levels help students to choose three subjects for year 13 in an informed way, particularly if they plan to drop a subject in the process.
They also provide encouragement in advance of university applications for “bright but under-confident” candidates, as well as offering recent exam results to boost their applications.
“Our admission goal remains to select the best students, regardless of their educational regime,” Dr Sewell said in the correspondence.
“We are committed to ensuring that no student is disadvantaged within our processes by the model of provision offered by their educational institution.”
The plan to separate AS and A levels has proved controversial, with universities, headteachers and MPs all expressing concerns.
It is not the first time that Cambridge University has spoken out on the issue. It previously warned that AS levels were the best predictor of how well a student will perform in every subject except maths, and argued that they encouraged more disadvantaged students to apply to its degree courses.
Labour has suggested it would reverse the move and link AS and A levels, if it comes to power.
Martin Doel, chief executive of the Association of Colleges, said: “Cambridge University is absolutely right to lead the calls for their retention. The whole education system should be working together to protect these valuable qualifications.”
A Department for Education spokeswoman said AS levels were an “unnecessary burden” on teachers and students.
“Students will still be able to sit an AS before deciding whether to take a subject at A level, but will no longer be required to do so,” she said.