Amy Jones, Maths Subject Advisor

As a teacher, targeting misconceptions in the classroom was an important part of my day. Whether I was marking homework or looking at solutions on mini whiteboards, I would be looking out for any common incorrect answers, to get insight on which parts of the lesson students were struggling to understand.

In this blog, I’ll look at some common themes from our GCSE (9-1) Maths examiners, to give teachers an idea of misconceptions which could be worth targeting in the classroom. Tackling these can be tricky sometimes, as it’s easy to fall back on old, familiar habits, so I’ve also shared a few ideas on how to help students correct their misconceptions.

Geometry and measures

In this topic, the common misconceptions pointed out by examiners are themed around accurate recall of knowledge, for example angle facts or area formulae. These are relatively straightforward to spot, as generally little interpretation is needed to figure out the underlying misunderstanding from the mistake.

When helping students with recall, it might be useful to look towards other subjects that need a lot of memorisation, such as dates in history or vocabulary in languages. Techniques such as flash cards and spaced recall can help students to solidify the correct facts in their mind and help them correct past misconceptions.

“Some candidates thought angles in a triangle add up to 360 degrees.” – J560/05 Examiner’s report, June 2026

“Candidates very commonly calculated base × perpendicular height for the area of the triangle, without dividing by 2.” – J560/02 Examiner’s report, June 2025

Number

Having a secure grasp of the number strand in GCSE Maths is fundamental for students. Many of these skills are introduced earlier in the curriculum, then get built upon during Year 10 and 11. For teachers, it’s about trying to balance introducing new concepts to students, while making sure gaps in understanding are addressed.

A common theme throughout these misconceptions is when students showcase knowledge of a procedure and try to apply the process without fully understanding what the percentage or fraction means. Time conversions are another area where students can make mistakes, especially under exam pressure.

There are many ways of spotting these misconceptions in the classroom; I used formative assessment tools such as mini whiteboards and diagnostic questions. Putting examples such as ‘convert 240% to a fraction’ in the lesson starter, perhaps with some carefully chosen multiple choice options, can help get a snapshot of student understanding before moving on. For students who do not have a firm grasp on this, using a multiple representation approach, such as area models and fraction strips, can help them find an explanation which ‘clicks’ for them.

 “There were incorrect interpretations of 240%, with some candidates writing it as
2401000 
rather than 2.4 or 240100
  .” – J560/05 Examiner’s report, June 2026

“Many were unable to multiply a fraction by an integer here. The majority multiplied both the numerator and the denominator by 3, not recognising that this creates an equivalent fraction.” – J560/02 Examiner’s report, June 2026

“Candidates often struggle to convert between units of time. The most common misconceptions here were that 1 minute 15 seconds = 1.15 minutes and 2 minutes 5 seconds = 2.05 minutes.” – J560/05 Examiner’s report, June 2025

Algebra

Like the number section, one of the misconceptions highlighted by examiners indicate examples of students following a procedure that they are comfortable with, without recognising how that procedure fits with the question. Many students feel more comfortable manipulating an equation – they are more familiar with it, but candidates not recognising the need to provide their answer as an inequality perhaps indicates a lack of understanding of the question.

“It was very common for candidates to change this inequality into an equation that they then solved correctly, but they did not then change their answer back into an inequality and this lost them the mark.” – J560/02 Examiner’s report, June 2026

Mistakes in algebraic manipulation is another common area for misconceptions, with students confusing which terms are like, or skipping over terms when expanding brackets. The use of a visual framework is useful here, for example using an area model for expanding brackets. Similarly, using a grid method for expanding or factorising brackets can provide a scaffolded ‘fill-in-the-gaps’ approach. Physical tools such as algebra tiles can be helpful for teaching students how to collect like terms.

 “A common error here was incorrect expansion of (x + y)². Many wrote that (x + y)² = x² + y², omitting the 2xy term. Another frequent error was in collecting like terms, with responses such as x² + x² = x⁴” – J560/02 Examiner’s report, June 2026

More examiner feedback

After every exam series, we publish examiner reports for each of the GCSE (9-1) papers, which are designed to give teachers insight into how students have performed. They include commentary on each question highlighting common mistakes and identifying areas of strengths/weaknesses. You can access them via our secure teacher platform, Teach Cambridge.

Other avenues of post-exam feedback are available too, such as the upcoming Exam Review professional development sessions, or autumn teacher networks.

Stay connected

If you have any questions, you can email us at maths@ocr.org.uk or call us on 01223 553998. You can also sign up to subject emails to keep up to date with the latest news, information and resources.

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About the author

Amy joined Cambridge OCR in 2023 after teaching for five years in both state and independent schools. She provides support across all the Cambridge OCR Maths qualifications, but with a focus on GCSE, A Level Maths and Further Maths. She graduated from the University of York with a degree in Mathematics and Economics before gaining a PGCE in Secondary Mathematics and an MA in Education.