Many MYP students reach the investigation in Grade 9 or 10 and find a pattern that works for the first few cases. They write it down, feel relieved, and then lose marks because the pattern was never proven for every case, or because the working is correct but the reader cannot follow it. That gap between getting the right answer and explaining it clearly is where most Criterion B and Criterion C marks are lost, and it is very fixable.
The short answer is that Criterion B rewards a pattern you can justify for all cases, not just the ones you tested, and Criterion C rewards writing that a stranger could follow without asking you a single question. Improving both comes down to a few habits practised regularly: testing a conjecture on purpose, naming the rule in your own words, and reviewing your work as if you were the examiner.
Why Criterion B stalls after the first pattern
Most students are good at spotting patterns. The trouble starts when they stop too early. A table of values lines up, a formula fits the first five rows, and the investigation moves on. Examiners look for something more: a conjecture that is tested with cases chosen deliberately, including awkward ones, and then a reason why it should hold.
Move from 'it works' to 'it always works'
Try this with every pattern you find. Write the conjecture as a sentence, then ask what would break it. Pick the smallest, largest and strangest inputs you can think of, such as zero, negatives or a case where two rules overlap. If the rule survives those, say so. If it fails, you have just found a more interesting result to report.
Once the rule holds, try to explain why. A short algebraic argument, a diagram or a simple counting reason is enough. Even a partial justification shows the kind of reasoning Criterion B is looking for, and it is far more convincing than a longer table.
Criterion C is about the reader, not just the answer
Criterion C is the one students most often underestimate. Many strong mathematicians write in shorthand that makes sense only to them. They skip a step because it feels obvious, use a symbol without defining it, or put a final answer at the bottom of a page of scribbles with no signposting.
A simple test helps. Read your investigation aloud, or hand it to a classmate who did not do the work. Ask them to point to where your conjecture is stated, where you tested it, and where your conclusion begins. If they hesitate, your writing needs headings, labelled diagrams or a sentence that links one step to the next. Command terms matter here too: if the task says 'justify', give a reason, not just a result.
- State your conjecture clearly before you test it.
- Define any variable or notation the first time you use it.
- Use a labelled diagram or table where it saves words.
- End each section with one line saying what you have just shown.
A weekly routine that builds both criteria
Improvement comes from small, regular practice rather than one heroic weekend before the deadline. A routine that works well for many students looks like this:
- Spend one session on a short pattern-spotting problem, and write a conjecture before doing any calculation.
- Test it with three deliberately chosen cases, and note which one you expected to fail.
- Rewrite one paragraph of an earlier piece of work so that a reader can follow it without help.
- Keep a running list of the command terms your teacher uses, with an example of each in your own words.
Keep the sessions short, around forty-five minutes, and review them every fortnight. You will notice that your conjectures become sharper and your explanations shorter and clearer, which is exactly what both criteria reward.
How a small batch and criteria-aligned teaching help
Feedback is what turns practice into progress, and it works best when it is specific. In a large class it can be hard to get a detailed comment on every investigation draft. At INACADEMICS, batches are kept to four to eight students, so our teachers can read each student's draft, point to the exact sentence where the justification is missing, and check it against the MYP Mathematics rubric for the criterion in question.
Our teachers are subject specialists who know the assessment criteria well, so feedback is tied to what the rubric actually asks for rather than general advice about maths. A student who finds a pattern but cannot justify it gets help building the argument. A student whose working is correct but unclear gets help structuring the write-up. Parents receive regular updates tracked against each student's plan, so you can see which criterion is improving and which still needs attention. If your child is following the MYP route, you can read more about our IB MYP tuition programme for Grades 8 to 10.
If you are not sure where your child currently stands, the simplest first step is a conversation. You can also find more practical guides on the Inacademics blog, including ideas for other subjects and assessments.
Frequently Asked Questions
How can my child tell whether Criterion B or C is the weaker one?
Look at the feedback on returned work. If comments mention a missing generalisation, untested cases or no justification, Criterion B is the likely issue. If the maths is right but comments say the working is hard to follow, unclear or unlabelled, Criterion C needs attention. Many students need work on both, and a short diagnostic can confirm it.
Does a longer investigation score higher?
Not necessarily. Examiners reward clear reasoning, deliberate testing and a well-justified conclusion. A focused report that explains one pattern thoroughly often scores better than a long one full of unexplained tables. Spend your effort on quality of argument rather than on volume.
How does INACADEMICS help students improve these criteria?
We start with a short diagnostic and a plan for each subject, then place students in small batches of four to eight. Teachers give feedback against the MYP rubric, students practise with weekly worksheets and monthly mocks, and parents receive regular updates tracked against the plan. The aim is steady, visible progress on the criteria themselves.
When should we start working on these skills?
As early as possible in the MYP years, ideally before the first major investigation. Building the habit of testing conjectures and writing for a reader takes time, and it is much easier to develop gradually than to fix in the weeks before a deadline.
Wrap-up and next steps
Criterion B and Criterion C are learnable skills. Test your patterns harder, justify them properly, and write for a reader who was not in the room. With regular practice and specific feedback, most students see clear improvement within a term. If you would like to talk through your child's current work, you can book free counselling by calling or messaging us on WhatsApp at +91 9014010410, or visit us at 117, 1st Floor, Raichandani Business Bay in Kokapet, above Karachi Bakery.