Modular exams in A-level science subjects should all be taken during the summer term to avoid disruption to learning and unnecessary re-sits, a review of science and maths education has recommended.
The Government-commissioned document also called for exams to test pupils' in-depth problem- solving skills and understanding of scientific concepts.
There should also be more emphasis on the use of accurate English when pupils' science knowledge is assessed, it said.
The report, from the independent Science and Learning Expert Advisory Group, also expressed concerns over the inadequacy of the maths content of the science 14-to-19 curriculum, particularly A-level chemistry and maths.
Sir Mark Walport, group chair, told The TES that "still more still needs to be done" to ensure curriculum and assessment allowed for in-depth study and wider understanding.
He also called for the setting up of "expert groups" from across the science world to advise on the science curriculum and its assessment.
The review claims there is "widespread concern" in the science and teaching communities about the qualifications system.
It said: "This provides compelling evidence of a significant gap in perceptions and engagement between the specialist organisations which design and deliver qualifications, and the science and teaching communities which provide education."
The report, Science and Mathematics Education for the 21st Century, also highlighted the need to provide highly trained teachers, sometimes with industry experience, to inspire pupils.
Schools should also "make greater use of current recruitment and retention pay flexibilities" to increase recruitment and retention.
To compel headteachers to put more emphasis on subject-specific training, they should have to report back to governors on exactly how and when their science and maths teaching staff were receiving continuing professional development.
As part of a programme of increased accountability, it said the responsibility for science and maths enrichment programmes should be devolved to schools, and heads held accountable.
Specialist science and maths schools should have to produce an annual report for Ofsted on how the school is delivering the subjects.
The report has been widely welcomed across the science community.
Sir John Holman, director of the National Science Learning Centre in York, said he supported the drive for a greater emphasis in maths for science students.
"But I would go further and call for every post-16 pupil to study for some kind of maths qualification."
Sylvia McNamara, director of policy implementation at the Qualifications and Curriculum Development Agency, said: "We are introducing more stretch and challenge in these subjects and this is reflected in recent changes to the design of qualifications."
Association of School and College Learners policy director Malcolm Trobe welcomed many of the report's recommendations, but added: "Great care needs to be taken in increasing the amount of maths in A-level sciences as this runs a real risk of reducing the take-up of these courses.
"The modular approach has a major motivational impact on lower-attaining students and we would not want to see this option disappear."