When you say 90-95% needed for Tiffin Boys, if the paper has 80 questions then I think that's quite a broad margin of error - 5% = 6 questions.

Do the schools you're interested in use standardised scores or age standardised scores? This makes a difference to the calculations. Stressedparent's examples show standardised scores. The nfer website states:

**Quote:**

However, in order to allow for the differing ages of the pupils as accurately and as fairly as possible across the complete score range, the age-standardised scores are calculated in a much more statistically complex way, although the effect is similar to computing sets of scores using the above equation for pupils of the same age (to the nearest month).

(The above equation referred to is the one in stressedparent's post.) As stressedparent says, it depends on the cohort for each test. So in order to get the age st'd results you would need to know each child's score and also their month of birth. This is why no one can say that x% is a definite st'd score but that x% represents an approximation/guide to the scores you need to achieve.

Hope this has not muddied the waters further...