ISEB Common Pre-Test Scores Explained: SAS, Percentiles and IQ

The ISEB Common Pre-Test is a set of four adaptive online tests that many independent senior schools use as part of admissions, and its score is a Standardised Age Score (SAS) with an average of 100. Parents who search for "what is a good ISEB score" find no answer from ISEB, because the organisation publishes no pass mark and does not release results to families. This guide sets out what ISEB does say in its own documents, how the score is built, why the average of 100 does not mean the same thing as an IQ of 100, and what a family can reasonably do with a number.

What is the ISEB Common Pre-Test?

ISEB Limited describes the Pre-Tests as a set of four online, adaptive entrance assessments: English, mathematics, verbal reasoning (VR) and non-verbal reasoning (NVR), all multiple choice. Its 2026-27 framework says they are designed for pupils in Years 6 and 7. Most children sit them once in Year 6 for Year 7 entry (11+), and ISEB's families page says some senior schools, such as Eton and Harrow, use them as a precursor to Year 9 entry (13+). They can be taken at the pupil's current school, at the senior school applied to, or at an approved independent invigilation centre anywhere in the world, and a pupil can sit them only once in an academic year.

The full sitting takes 2 hours 15 minutes. At standard time the invigilation script gives English 40 minutes, mathematics 40, non-verbal reasoning 30 and verbal reasoning 25, which adds to 135 minutes; with 25% extra time the figures become 50, 50, 37.5 and 31.25 minutes. Live testing for the 2026-27 session starts on 1 September 2026 and ends in late May 2027, although the framework PDF says tests can be taken between the beginning of October and the end of June, so check dates with the school.

Adaptive means the next question depends on the last answers. ISEB says each test section has several question pools, each with a minimum and a maximum number of questions, and that pupils who answer correctly are tracked to harder content. It publishes no question totals. It also says the tests are not speed tests: "Pupils do not achieve a higher score for answering more questions", and the result comes from accuracy and consistency. The system does not let a pupil go back and change an answer. For practice material with the same kinds of items on this site, see our verbal and spatial IQ tests.

How is the ISEB Pre-Test scored?

The headline result is the Standardised Age Score. ISEB's school page defines it as a score based on the accuracy of a pupil's answers and their consistency, "adjusted for age and placed on a scale which makes a comparison with a standardisation sample taken from the independent schools' sector (the average is 100)". A support article adds that the scale has an average of 100 and a standard deviation of 15, so that around 67% of pupils score between 85 and 115, 16% score over 115 and under 5% score more than 130. Comparisons are made with pupils of the same age, which ISEB says means no disadvantage for younger children or those who test earlier in the window.

Schools see more than the SAS. Each applicant's report includes a stanine, a percentile rank and a group rank, together with a mean SAS, and ISEB says the percentile rank and stanine are based on the SAS, using different numeric ranges. If the SAS is roughly normal within its norm group, as the stated mean and standard deviation imply, then within that group (our arithmetic):

• SAS 85: about the 16th percentile
• SAS 100: the 50th percentile
• SAS 115: about the 84th percentile
• SAS 130: about the 98th percentile (97.7)

Two details are worth noticing. A normal curve puts 68.3% of people between 85 and 115 and 15.9% above 115, close to ISEB's statements, but only 2.3% above 130, so "under 5%" is true but loose. And the percentile rank applies to the independent-school sample, which brings us to the main question. For the same kind of score on a different test, see CAT4 scores explained, and for the US counterpart, ISEE scores explained.

What is a good ISEB Pre-Test score?

There is no ISEB answer. Its support page says that the Pre-Tests "do not have grades or even a pass mark (as all of this is dependent on the school which uses the tests)", and ISEB recommends parents ask the school for context. ISEB does not release results to parents, so a family sees a result only if the school chooses to share it. We found no published cut-off for any school. The pages say schools use the results as part of their admissions process; we found nothing on how any particular school weights the score against interviews, references or other tests. For a US high-school entrance exam that reports an IQ-style quotient, see HSPT scores explained.

Is the ISEB Pre-Test an IQ test?

ISEB does not call it one. The words IQ, intelligence and CAT4 do not appear in the ISEB pages and PDFs we read. It says the Pre-Tests are designed to identify attainment and potential: English and mathematics follow topics taught in class, while verbal and non-verbal reasoning let pupils show "academic potential" through question types that may be unfamiliar to them. That is the same split we describe for achievement tests and IQ tests.

The score scale looks like an IQ scale, with a mean of 100 and a standard deviation of 15, which invites the comparison. It does not carry over, for a reason ISEB states itself: the reference group is a sample from the independent schools' sector. A pupil at the 50th percentile of a group of applicants to selective schools would sit above the 50th percentile of all children of that age, and ISEB does not say by how much. It also publishes no size or year for its standardisation sample and no reliability figure that we could find. We found no ISEB comparison with CAT4 or with 11+ scores, and there is no published conversion to IQ. If you want to read an SAS against the whole population, treat any such figure as a guess, and use our IQ percentile calculator only to translate a score into a percentile on a normal curve. The same warning applies to 11+ standardised scores.

Practice, retakes and invalid sittings: what ISEB says

ISEB says a pupil can sit the tests only once in an academic year, and that in the very unlikely event of a second sitting, "the first set of results will stand". A test that is abandoned is recorded by the invigilation centre on a Centre Declaration Form, and ISEB says this makes senior schools aware when they view the results. For practice, ISEB says it cannot guarantee the accuracy of third-party practice resources that it does not endorse, and that such material may not reflect the presentation, difficulty, content and scoring of the live tests. It names Bond Online Premium Plus as the only preparation platform it endorses. If you are weighing the value of practising at all, our report on the practice effect on cognitive ability tests reviews what repetition does to scores, and ISEB publishes separate SEND guidance for adjustments.

What should a family do with an ISEB result?

• Ask the senior school what the result means for its own admissions, because ISEB sets no pass mark
• Read the SAS as a position among independent-school applicants, not among all children
• Remember the score is age-adjusted and based on accuracy and consistency, not on how many questions were answered
• Do not convert the SAS to an IQ; ISEB publishes no conversion, norm size or reliability figure
• Treat any single score as an estimate with a margin of error, as described in our guide to the margin of error

The IQ Metrics test reports on the standard IQ scale against the general population, which is a different comparison from an admissions sample. For a child, see the kids IQ test and our guide to IQ testing for children, and for how selective programmes use scores, universal screening in gifted programmes.

Common questions