The Mistake That's Costing Students 10–20 Marks Every Exam

Direct Answer: What Is This Mistake?

The single most mark-costly mistake in Singapore secondary Math exams is not a wrong formula or a misread question — it is incomplete or missing working. Students who skip steps, rush through solutions, or write only the final answer lose method marks on every single question where they make an error. Across a full paper, this silently accumulates to 10–20 lost marks.

Why This Is So Damaging

Singapore's O Level and N Level Mathematics marking schemes award marks for correct method even when the final answer is wrong. This means that a student who sets up the equation correctly, applies the right formula, but makes an arithmetic error at the last step can still earn 70–80% of the marks for that question — if the working is shown.

When working is not shown, the examiner can only mark what is on the page. A wrong final answer with no working scores zero. A wrong final answer with clear, correct working can score 2 out of 3 marks. Across a 100-mark paper with 20+ questions, the difference can easily exceed 15 marks — the equivalent of an entire grade boundary.

Signs Parents Should Look Out For

• Answer scripts that show only final answers with no steps in between

• Your child's exam paper shows multiple questions scoring 0 out of 3 or 0 out of 4

• Teacher feedback mentions "no working shown" or "method not demonstrated"

• Your child says they do the working "in their head" to save time

Common Related Mistakes

• Writing the formula but substituting values incorrectly without showing the substitution step

• Jumping from the question directly to the answer in multi-step problems

• Not labelling intermediate results (e.g., writing x = 5 without stating what x represents)

• Crossing out correct working in a panic and replacing it with a wrong method

The Educational Psychology Explanation

Students avoid writing working for several psychologically understandable reasons. The first is time pressure — they believe that skipping steps saves time. Research in educational psychology consistently shows the opposite: students who skip working spend more time re-reading and re-attempting questions because they lose track of where they are in the solution.

The second reason is fear of being wrong. When a student writes full working, they feel exposed — each step is visible for judgment. When they write only the answer, they feel they can attribute a wrong answer to a slip rather than a misunderstanding. This self-protective behaviour, described in self-determination theory by Deci and Ryan (1985), actually makes performance worse over time.

What Students Should Do

1. Make a firm rule: no final answer without at least two visible working steps. Every time, without exception.

2. Practise laying out solutions as if teaching someone else. Your working should be readable by another student.

3. When checking, verify each line of working — not just the final answer.

4. Never cross out working unless you are certain it is wrong. Crossed-out correct working cannot earn marks.

What Parents Should Do

1. Review exam scripts together and specifically look for questions where marks were lost due to missing working.

2. Ask your child to explain their working to you. If they cannot, there is a deeper understanding issue to address.

3. Ensure Math tuition Singapore sessions include working-out practice — not just answer checking.

Real-Life Student Example

Alvin was a Sec 4 G3 student who came to Math Lobby in Term 2 with a score of 56 from his school's preliminary examination. When we reviewed his paper, we found 17 marks lost from questions where his working was either absent or incomplete. In 11 of those cases, his method was entirely correct — only the final step had an error.

We focused on one thing for three weeks: writing full, clear working for every practice question. In his next school test, he scored 71. The math had not changed. The habit had.

Key Takeaways

• Missing working is the single most mark-costly habit in Singapore Math exams

• Method marks are awarded even when the final answer is wrong — but only when working is visible

• Full working does not waste time — it saves it, by keeping the student on track

• This is a habit — and habits are trainable

Frequently Asked Questions

Do Singapore Math exams award marks for working?

Yes. Both O Level and N Level Math papers award method marks. A correct method with a wrong final answer can still earn 2 out of 3 marks. This makes full working essential, not optional.

How much working should a student show?

Enough that a marker can follow the logic without guessing. Every formula substitution, every simplification, every conclusion should be explicit. If you skip a step, ask yourself: would a marker understand why?

My child says showing working takes too long. Is this true?

No. This is a common misconception. Students who regularly practise showing working become faster at it — and they make fewer errors because writing each step forces them to slow down and check their logic.

Should I look at my child's exam script to check for working?

Yes, absolutely. Ask the school for returned papers. Look not just at what was wrong, but at how much working is shown. A pattern of missing working is one of the most actionable things you can fix.

Can Math tuition help my child develop better working habits?

Yes. Quality Math tuition Singapore sessions will insist on full working for every solution, review it line by line, and train the habit until it becomes automatic. This is one of the fastest ways to recover lost marks.

Not sure why your child keeps making the same Math mistakes? At Math Lobby, we help students understand not just what went wrong, but why it happened — and how to prevent it from happening again. Book a trial class today and discover a smarter way to learn Mathematics.