Assessment Ideas for Percentages and Interest: Rubrics, Tasks and Mark Schemes (Ireland, Leaving Certificate)

Percentages and interest are among the most useful things we teach — and among the easiest to assess badly, because a student can get the right answer by a memorised trick while understanding nothing. Good assessment probes reasoning, not just outcomes. This article sets out formative and summative options, a sample mark scheme in prose, quick checks and exam-style tasks for percentages and interest, written for classes working within the Leaving Certificate curriculum set by the NCCA and the State Examinations Commission (SEC), where these skills underpin the applied questions at Ordinary and Higher Level.

Quick formative checks

Frequent low-stakes checks tell you who has the concept and who has a fragile trick. Keep them short and diagnostic.

• Mini-whiteboards: "Increase €80 by 15%" — everyone shows at once, and you spot errors instantly.
• Odd-one-out: three methods for finding a percentage; students identify which is wrong and explain why.
• Reverse it: "A jacket costs €69 after a 20% reduction — what was the original price?" to test whether they truly understand the multiplier.
• Compound vs simple: a quick check that students can say, in words, how the two differ before they calculate.

The tasks in Percentages and Interest – Everyday Mathematics give you graded questions you can lift straight into these checks, with real-world contexts — savings, VAT, discounts — that keep the maths grounded.

A summative task worth setting

For a summative judgement, use a short structured problem set that moves from routine calculation to applied reasoning: a simple percentage change, a reverse-percentage problem, and a multi-step compound-interest question on a savings scenario in euro. This mirrors how the SEC layers difficulty within a single question. Ask students to show method, because that is where partial marks live.

A sample mark scheme in prose

Describe the bands so students internalise them. A top response chooses an efficient method (a single multiplier rather than repeated steps), lays out working clearly, carries units and euro signs correctly, and interprets the answer in context ("so the saving is €12"). A secure middle response reaches correct answers on routine parts but relies on longer additive methods and stumbles on the reverse-percentage step. A developing response can find a straightforward percentage of an amount but confuses percentage change with percentage of, and treats compound interest as simple interest. Sharing these descriptions before the task tells students exactly what "showing method" earns them.

Exam-style tasks and cross-topic links

Percentage reasoning rarely appears alone in the exam, so assess it alongside related skills. A task that combines interest with area or measurement — costing the tiling of a room, say, at €24 per square metre — lets you draw on The Pythagorean Theorem – Applications for the measurement and percentages for the pricing, which is far closer to how applied questions actually read. Context matters for engagement too: framing tasks around genuine Irish situations students recognise — mobile-phone plans, credit-union savings, sale reductions in euro — makes the maths feel purposeful rather than abstract, and it mirrors the everyday problem-solving the SEC favours. Because fluency with the underlying number work is what holds students back most, a diagnostic drawing on Fractions Complete – Grades 6 to 7 is worth running early: students who cannot move confidently between fractions, decimals and percentages will always find interest calculations harder than they need to be. Timed exam-style practice, marked against the bands above, then turns secure understanding into reliable marks.

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