What the diagnostic measures
Three layers of evidence, all built from the same adaptive engine that powers the practice journey.
Mastery per topic
What the child has secured at each level of the National Curriculum. ‘Year 5 fractions: comparing fractions secure, fractions of amounts drifting’ — at that level of detail.
Misconceptions surfaced
Specific named misconceptions — ‘adds numerators and denominators’, ‘confuses fronted-adverbial commas with parenthesis commas’ — not generic ‘fractions error’ labels.
Prerequisite gaps
Where a topic is failing because the prerequisite is weak. Often the most useful signal — fixing the prerequisite resolves three or four downstream topics at once.
Year-on-year drift
If the child has used Northstar before, the diagnostic compares against previous evidence. Drift gets named directly: ‘was secure on this in Year 4, has slipped in Year 5’.
How adaptive sampling works
A SATs-style mock paper asks every child every question. That's fair, but it's slow — and most of the questions don't tell you anything new. Adaptive sampling does the opposite: the diagnostic asks the FEWEST questions that maximise information. If a child gets the first three Year 5 fractions questions right, the engine doesn't ask three more — it moves on. If a child slips on a calibration question, the engine asks two follow-ups to pin down the misconception. The result is a 15–20 minute experience per subject that produces more diagnostic detail than a 60-minute mock paper. Most KS2 children sit it in one session; younger children can split across two.
What you get when it's done
A diagnostic report sent the same day, and a personal route through KS2 built from the result.
Diagnostic report
Per-subject summary of mastery, misconceptions, and prerequisite gaps. Includes sample questions the child answered (and the explanation they saw).
Personal practice route
Adaptive practice journey built from the diagnostic. The next question your child sees is the one the engine thinks will help most.
Weekly progress
Once practice starts, weekly summary emails show what's been mastered + what's drifted since last week.
SATs-readiness plan
Year 6 children get a per-paper SATs plan from the diagnostic — Arithmetic, Reasoning, Reading, SPaG, with the specific topics to focus on.
Diagnostic by subject
The same diagnostic shape, three subjects. Each takes 15–20 minutes for a typical KS2 child.
Maths
Number, place value, arithmetic, fractions, decimals, percentages, ratio, algebra (Y6), geometry, measurement, statistics.
Reading
Retrieval, inference, vocabulary, evidence, structure and authors' craft. Real KS2-graded passages, not generic passages.
SPaG
Word classes, sentence types, apostrophes, commas, modal verbs, tense, agreement, direct speech, relative clauses, cohesion. Aligned to the SATs SPaG paper structure.
Free, no card, no exam-room
The diagnostic is the free tier — every Northstar account gets it, no card required. It runs in a calm interface (not a mock-paper format), so children don't sit it with exam anxiety. The result is the same evidence a school would generate from a half-term of marking — without the marking, and on the day.
Frequently asked questions
Is the diagnostic really free?
Yes — every Northstar account includes the diagnostic + the practice journey built from it. No card required, no trial expiry. Premium tiers (Parent Max, Teacher Max, School Max) add depth — more practice volume, fuller parent reports, school-wide dashboards — but the diagnostic itself is always free.
How long does it take?
15–20 minutes per subject for a typical KS2 child. Younger children (Year 2–3) often split it across two sittings; older children usually sit it in one go. There's no time limit — the engine adapts, not the clock.
How accurate is the diagnostic?
More accurate than a mock paper for the same time invested, because adaptive sampling spends every question gathering new information. Comparable to a half-term of teacher-marked evidence — without the half-term. Limitations: it can't replace a SEND-specialist assessment, and it tells you what the child can do now, not what they will be able to do after teaching.
Do I have to do anything during the diagnostic?
No — children sit it on their own, at home or in school. Each question has a calm explanation after the answer, so they're learning while they're being assessed.
Can I see the diagnostic report?
Yes — the report is in the Parent dashboard the moment the diagnostic finishes. Teachers see the same shape at the class level.
What happens after the diagnostic?
The engine builds a personal practice journey from the result. Your child opens Northstar each day and the next question is picked for them. The diagnostic refreshes automatically every six weeks so the practice stays aligned with current evidence.