ISEB Common Pre-Test explained: Format, scoring and what schools see
The ISEB Common Pre-Test is an online, adaptive admissions test used by many of the UK's leading independent senior schools as part of 11+ or 13+ entry. ISEB does not publish a current subscribing schools total on its public site, but recent published counts have sat around 80 senior schools. Your child sits it once per year, the schools you've applied to share the same result, and the score follows them through the rest of the admissions process at each school.
This guide covers what's in the test, how the adaptive engine and standardised age scoring (SAS) work, what a school sees at their end when the result comes through, and the few things that help with preparation. The deliberately short version: It's a screening tool, not a final exam, and many schools combine it with at least one other assessment.
What's in the test
The Pre-Test is made up of four separate tests, sat on a computer, all multiple choice. The four subjects are English, maths, verbal reasoning and non-verbal reasoning. Your child can sit all four in one sitting or split them across multiple sessions, depending on the school or test centre.
| Test | Approximate length | What it covers |
|---|---|---|
| English | ~40 minutes | Reading comprehension, grammar, spelling and punctuation |
| Maths | ~40 minutes | Number, geometry, measurement and data, up to Year 5 of the National Curriculum |
| Verbal reasoning | ~25 minutes | Word relationships, analogies, codes, vocabulary in context |
| Non-verbal reasoning | ~25 minutes | Pattern, sequence and rotation puzzles using shapes and figures |
The English and maths tests sit broadly inside Key Stage 2 content up to the end of Year 5, so the curriculum is already familiar from school. The verbal and non-verbal reasoning tests aren't part of the National Curriculum, which is the bit many parents worry about. They're question formats your child probably hasn't seen in primary school unless they've done some 11+ prep, and that unfamiliarity is exactly what familiarisation work helps with.
How the adaptive test works
Each of the four tests is adaptive. After every question, the system updates its estimate of your child's ability and picks the next question to be the most informative at that level. Get a run of questions right, the engine moves them up to harder material. Get a run wrong, it brings them back down. Two children sitting the same test will almost certainly see different questions and a different total number of questions.
Pupils can't go back to change a previous answer. Once the engine has used the response to choose the next question, the answer is locked. It's worth telling your child this in advance so they don't waste energy worrying about it on the day.
In practical terms, this means your child should answer every question as carefully as they can, even when one feels harder than the last. A harder question usually signals the engine has them on the right track, not that they've made a mistake. Encouraging your child to slow down on hard questions tends to be better advice than 'just guess and move on'.
Standardised age scores, explained
ISEB doesn't report a raw mark. Schools receive a standardised age score (SAS) for each of the four tests. The SAS is built on a normal distribution: the average is 100, the standard deviation is 15, and the score is adjusted for your child's age in months. A summer-born child and an autumn-born child who answer the same questions correctly will not get the same SAS, because the engine accounts for the age gap.
What the numbers translate to in plain English:
| SAS range | How many children | What it tends to mean |
|---|---|---|
| Below 85 | Lowest 16% of the cohort | Below the typical independent-school threshold |
| 85 to 99 | Below the cohort average | Some subscribing schools may still consider, with strong evidence elsewhere |
| 100 | Cohort average | Average score across the standardisation sample |
| 110 to 119 | Top ~25% | Competitive at most subscribing schools |
| 120 to 129 | Top ~10% | Strong; clears the sift at most schools |
| 130+ | Top ~2-3% | Very high; clears the sift at the most oversubscribed schools |
A few things worth knowing. The standardisation sample is taken from the independent schools' sector, not the wider Year 6 population, so a 100 isn't the national average of all Year 6 children. It's the average of children sitting independent senior school pre-tests. That makes a 110 more competitive than it might first sound.
What schools see at their end
Subscribing schools receive a report for each candidate showing the SAS in each of the four tests and a profile across the cohort. They don't see which specific questions your child answered correctly, because the adaptive engine selected different questions for each child. They see enough to compare like-for-like across applicants and enough to spot whether a child is unusually strong or weak in one area.
Parents don't receive the SAS directly. The most you'll typically see is whether your child has been invited to the next round or, eventually, whether the offer comes through. Some schools will share scores informally on request, especially if your child wasn't offered a place and the school feels feedback is owed. It's worth asking, but don't assume.
If your child is applying to multiple subscribing schools, the same SAS is shared with all of them automatically. Your child sits the test once, in one window. There's no benefit to retaking it within a year, because the system blocks repeat attempts.
When and where children sit it
Most subscribing schools test in Year 6, usually between September and December. A few test in Year 7 instead, particularly some 13+ entry schools that want a more current picture. The senior school confirms the window when you register, and arranges the test centre too. Many children sit it at their own prep school during the school day; others travel to a regional ISEB-approved centre.
From the 2022–23 cycle, registration is completed by the pupil's parent or guardian directly via the ISEB Guardian Portal, not through the prep school. The Pre-Test itself is free for families, and the prep or invigilation centre is only the venue for sitting the test rather than the registration channel. The senior schools and ISEB between them cover the cost.
What helps with preparation
The short version: Familiarisation matters more than coaching. The most useful thing you can do is make sure your child has seen the question types before, knows how the adaptive interface works, and isn't surprised by anything on the day. The two unfamiliar areas, verbal and non-verbal reasoning, deserve the most attention because they sit outside the school curriculum.
Sensible preparation steps
What tends to really help in the months before the Pre-Test.
- Work through a few practice papers in each of the four subject areas, so your child recognises the formats
- Use an online practice tool at least once, so the screen-based, click-to-answer format is familiar
- Spend more time on verbal and non-verbal reasoning than on English and maths, because they're the unfamiliar formats
- Build up to one or two timed full-length practice sessions in the month before the real test
- Talk through what happens if a question feels too hard (slow down, don't panic) so your child has a plan
- Keep the bigger picture in view: it's one of several signals each school uses, not a pass/fail moment
The thing that doesn't help, in our experience: drilling endlessly through past papers. Because the test is adaptive, the same papers won't come up. The questions are designed to probe a range of abilities, and any single set of practice questions covers only a slice of that range. A small amount of varied, well-pitched practice tends to beat a large volume of repetitive drilling.
