GCSEs and A-levels in science and geography are easier than they were 10 years ago, the exams regulator said today.
Standards have slipped, with teenagers often facing more multiple choice and short structured questions and papers with less scientific content, according to reports published today by Ofqual.
The watchdog conducted reviews of GCSEs and A-levels in biology and chemistry between 2003 and 2008 as well as A-level geography between 2001 and 2010 and A-level critical thinking in 2010.
The findings show that among the GCSEs, changes to the way the exams were structured had "reduced the demand" of the qualifications, while the A-level reviews found that changes to the way papers were assessed had in many cases made them easier.
The A-level geography review found that the removal of coursework from the qualification in 2010 - which was usually a 4,000-word investigation - had made it "less demanding".
It also reveals that between 2001 and 2010, there had been a shift "towards human geography and away from physical geography", fewer subjects were covered and there were fewer chances to assess pupils' skills.
The review adds that in general, the geographical content of A-level geography had "softened" in 2010, and that harder topics, such as ecology or atmospheric systems, had been removed from exams or made optional.
GCSE biology was easier in 2008 than in 2003 because there were more short papers with multiple choice and short answer questions, Ofqual found.
This made it harder to discriminate between students and meant that top students had less chance to show their knowledge and abilities, the review said.
It added that reviewers were also struck by the "poor quality" of some questions, which sometimes included "trivial or irrelevant" information and "made-up words".
The A-level biology criticised WJEC, the Welsh exam board, for having a high percentage of short structured questions, which reduced the amount of information pupils had to read and take in. This made the papers "less demanding" although overall they were "sufficiently demanding for this level of qualification".
The CCEA exam board was over generous in its marking of some questions and had less demanding coursework, Ofqual added.
The A-level chemistry review found that the exams had become easier between 2003 and 2008, because the questions were structured differently.
"In 2008 there were more short answer questions, involving simple recall, and fewer questions that required students to formulate multiple-step responses.
"This resulted in able students having less opportunity to demonstrate their higher-order knowledge and thinking skills in their responses to questions."
The GCSE and A-level science qualifications reviewed are no longer taken by students.
In a statement, Ofqual said that GCSEs are due to be revised after the national curriculum review, which is under way at the moment, while A-levels are also set to be reviewed.
"We will use the findings from these reviews to inform the development of regulations for those new qualifications," the regulator said.
A Department for Education spokesman said: "Ofqual's reports show evidence of a gradual decline in standards and that the exams system as a whole falls short of commanding the level of confidence we need.
"In particular these reports show that in recent years not enough has been demanded of students, and that they are not being asked to demonstrate real depth and breadth of knowledge.
"It is good that Ofqual has already taken action to strengthen the science GCSEs and we are committed to restoring confidence in all GCSEs and A-levels as rigorous and valued qualifications which match the best in the world."