## Monday, April 11, 2011

### An Eleven Plus Prediction

“My child achieved 76% on a mathematics paper. Is this good enough for her to pass the eleven plus?

“It sounds as if she did very well at this stage. Was this the first test she did?”

“Oh, no. She does a paper every week. Her scores are about the same – but she is improving a little each week. I think she still has a long way to go.”

When the correlation between two tests is known, a child’s performance on one test can be predicted from his or her performance on another. We hope, for example, that the one test that is offered at the eleven plus stage will correlate highly with thetest or examination marks at the A Level or International Baccalaureate level.

The predictive ability of the eleven plus is never certain. The only way to be able to use the eleven plus as a true prediction tool is to have a perfect correlation with later examination results. We then reach a grey area. What about absence from school? What about your child joining a band? What happens if the school does not suit? There are many and varied variables that can affect the ability to use one set of results to be able to predict another.

We need to assume that there is a rectilinear relationship between the tests – in other words every thing has to be in a straight line. A normal curve of distribution is used in the eleven plus to find children with above average ability levels. Children of average or below level ability find it difficult to win a place at a grammar school. If there was, however, a perfect relationship between the tests then we could say that the predictive ability was `1’. With no correlation the score is `0’. Parents working on probability on eleven plus mathematics will recognise the use of `1’ and `0’.

One of our local grammar schools is Dartford Grammar. Mick Jagger (Seven O levels and three A levels) went to the school and became a famous person who played in a band.

Suppose we try to establish a correlation between passing the eleven plus and playing in a band. We may not achieve a perfect score of 1. Suppose we go a little further and try to correlate passing the eleven plus and going on to become an international rock star – who plays in band. Our chance of a perfect correlation may be even smaller.

When we are asked to predict future academic success in the eleven plus based on the results of an eleven plus practice paper – then the chances of a perfect correlation seem to slip into uncertainty.

Some of us, however, may be supremely grateful if our star pupil who reached 76% on a standard eleven plus practice paper went on to become a international star with seven GCSE passes and 3 A Levels..