Achievement data, relating to pupils’ exam performance as measured by contextually value-added (CVA) indicators, are now the key to inspectors’ overall judgement on the school.

Those receiving an inspectors’ grade of four in this area are therefore at risk of either being placed in special measures or being given a notice to improve. Advice seen by The TES suggests heads and school managers expecting to receive such a score should:

* Look for trends in the statistics that might indicate that results are improving.

* For secondary, consider highlighting KS2-3 contextual value-added statistics, if they are better than those for KS2-4.

* Show your school has the capacity to improve, based on rigorous self-evaluation. Evidence of recent gains could include improvements in teaching, exclusion and attendance rates, or the appointment of teachers with a clear focus on raising standards.

But be careful. Heads need to be able to demonstrate to inspectors that claims of future improvements are grounded in reality, or they risk being penalised for being over optimistic about their school.

Schools with questions about data have been advised by the Association for School and College Leaders to call its hotline, on 0116 2991122, or to get in contact with Ofsted’s statistics division on 08456 404045.

Primary or secondary members of the National Association of Head Teachers should call 01444 472472 and ask for Jeff Holman.

The Fischer Family Trust suggests that schools raise any concerns about data through their local education authority. Extra information can be found on the web at www.fischertrust.org.