Secondary Schools (GCSE and equivalent) Achievement and Attainment Tables 2006

Following a successful pilot in 2005, a KS2-KS4 CVA measure is being published for the first time this year for all maintained schools and non-maintained special schools included in this publication. CVA is not published for independent schools because the Department does not collect from them the pupil level information needed to calculate CVA. Further information about the pilot phase can be found in the 2005 Key Stage 4 CVA Pilot publication at http://www.dcsf.gov.uk/performancetables.

What is CVA ?

What do we mean by contextual value added?

The examination results attained by pupils provide important information about the performance of a school - for example, the amount getting 5 good GCSEs tells us how many are well prepared for advanced levels of study. But we know that every child is different and each will have their own learning needs: some will have to do a lot of catching up to get 5 GCSEs, for others 7 or 8 good grades will be relatively easily attained, and for some (perhaps with significant special educational needs) 1 or 2 qualifications might be a huge achievement. We therefore also measure the progress made by a pupil from one stage of their education to the next.

When comparing the performance of schools it is important to recognise the progress they have helped pupils make. Simple Value Added (VA), which was first published in the Achievement and Attainment Tables in 2002, did this by comparing the qualifications achieved in Year 11 against a pupil's starting point (or prior attainment) - the results attained in the KS2 tests in Year 6.

CVA is not very different from simple VA. The basic principle of measuring progress from the KS2 test to qualifications attained at KS4 remains the same. However, a number of other factors which are outside a school's control, such as gender, special educational needs, movement between schools, and family circumstances, are also known to affect pupils' performance. CVA therefore goes a step further than simple VA by taking these factors into account and thus gives a much fairer measure of the effectiveness of a school. That means that comparisons against other schools are more meaningful, for example, when comparing the performance of a school in a leafy suburb against the performance of one in an inner city area - both of which might face quite different challenges.

Contextual Value Added scores

We base each pupil's CVA score on a comparison between their best eight results at GCSE (and equivalent) - sometimes referred to as their capped point score - and the typical performance of pupils with similar characteristics and similar results at KS2. If their GCSE (and equivalent) results are better than the average achieved by similar pupils, the CVA will be positive; if they do less well, it will be negative. All individual pupil scores, positive and negative, are added together and an average produced for the school. That average is then adjusted to account for the amount of pupils in the year group to give the school level CVA score. This score is then presented as a number based around 1000. This indicates the value the school has added on average for its pupils, given what is known about the circumstances of its pupil intake.

A more detailed explanation of the statistical model and the calculations used to produce the CVA measures, can be found in the technical annex of this website at http://www.dcsf.gov.uk/performancetables. A detailed explanation of how to work out a pupil's best eight results can be found in the 'more information' section of this website.

Interpretation of a school's CVA score

The CVA section shows, for each school:

• the KS2-KS4 CVA score;
• the upper and lower limits of a 95% confidence interval;
• a coverage indicator; and
• the average number of qualifications taken by pupils included in the CVA calculation.

The coverage indicator shows the percentage of pupils at the end of KS4 included in the CVA calculation. This might not be 100% because we do not have the KS2 test results for some pupils - for example, because they were previously educated outside England. If the coverage is very low (below 50%) then the CVA score is not published because it does not properly represent the effectiveness of the school.

The CVA measure is shown as a score based around 1000. Scores above 1000 represent schools where pupils on average made more progress than similar pupils nationally, while scores below 1000 represent schools where pupils made less progress.

For each of the KS4 CVA measures, a measure of 1006 means that on average each of the school's pupils achieved the equivalent of one GCSE grade higher in one subject than the average attained by similar pupils. A score of 1048 means that on average each pupil achieved one GCSE grade higher in each of their best eight subjects than the average attained by similar pupils. Conversely, a score of 994 means that the school's pupils achieved one grade lower in one subject on average, while a score of 952 means that pupils achieved on average one grade lower in each of their best eight subjects.

What a school's CVA measure tells you ?

Confidence Intervals

The CVA measure is a statistical means of assessing the relative effectiveness of schools or pupil progress between KS2 and KS4.

CVA is, however, based on a given set of pupils' results for a particular test or examination paper on a particular day. A school could have been equally effective and yet the same set of pupils might have achieved different results on the day. And the school would almost certainly have shown slightly different results with a different set of pupils, even with the same levels of prior attainment. Hence, although the CVA is based on all pupils in the school cohort (not just a sample of them), this degree of uncertainty should be taken into account if interpreting the figures as estimates of a school's effectiveness.

The uncertainty of a CVA score as a measure of school effectiveness can be presented as a confidence interval. This is a range of scores within which we can be statistically confident that the "true" school effectiveness will lie. The degree of significance that can be attached to a school's CVA measure depends, among other things, on the number of pupils included in the calculation. The CVA methodology produces a 95% confidence interval (CI) to show the range within which we can be confident the CVA measure represents the overall effectiveness of a school at KS4. If a school cohort is large the width of the CI will be small, but if a school cohort is small the CI will be wide.

A school level CVA measure must always be interpreted alongside the confidence interval. Schools where the lower limit of the CI is above 1000 represent schools where pupils on average made significantly more progress than pupils nationally, while schools where the upper limit of the CI is below 1000 represent schools where pupils made significantly less progress. Examples are given in the box below.

Further information on calculation and interpretation of CVA measures and confidence intervals can be found in the technical annex of this website at http://www.dcsf.gov.uk/performancetables.

Contextual Value Added (CVA) Percentiles

The CVA percentiles give the distribution of CVA scores and show where schools are placed nationally compared to other schools, based on the CVA measure. There are three versions, which allow comparisons against: mainstream schools only; special schools only; and all schools (i.e. both mainstream and special).

Snake plots are a useful way of presenting percentiles. The following three plots simply repeat the information shown in the table above but in a way that enables the national distribution to be more easily understood.

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