OBJECTIVE measures are not affected by the views, opinions, values and prejudices of the people making the measurements.

It seems self-evident, then, that objective measurement must inevitably be better than subjective judgments. True - but only up to a point. It very much depends on what is being measured.

If you want to measure the performance of an athlete or a formula one driver then their time over 100 metres or position in the drivers’ championship table at the end of a season are good objective measures of performance.

But the job of a headteacher is much more complicated than this. It involves supporting, motivating and monitoring staff; relating to children, parents, governors and inspectors; allocating and managing resources (financial and otherwise) fairly and effectively; strategic planning and curriculum development. And that’s just on a Monday morning!

How on earth can any of that be measured objectively? Perhaps national key stage test results and pupil absenteeism figures are objective measures of a head’s performance. They are certainly objective. But whether they are directly attributable to the performance of the head is a highly subjective judgment. They might be due almost entirely to the efforts of the class teacher who has performed miracles in spite of a total lack of interest and support from the head. They might, on the other hand, be a consequence of an enormous amount of support and encouragement the head has given to a comparatively weak teacher.

The fundamental point is that the final judgment about a head’s performance is, inevitably, a very subjective one. And we should not feel guilty or apologetic about this. There is nothing intrinsically wrong with subjective judgments - especially when there is no alternative.

Subjective judgments are bad only when they are based on ignorance, prejudice, biased information, hearsay and faulty reasoning; when they are contradictory, perverse and capricious. So instead of pretending that we can avoid subjectivity we should recognise that it is inevitable and concentrate on making our judgments well-informed, consistent and fair. We should be able to make a well-argued justification that the judgments, however subjective, are a true reflection of the actual performance of a headteacher. The technicl term for this is “validity”.

Validity is the extent to which a measurement actually measures what it is supposed to measure. An objective measurement might not be valid at all - if it were measuring something peripheral like the carpet in the head’s study. Key stage test results might be just as peripheral to the head’s performance, and so just as invalid. How then do we get a handle on those seemingly intangible qualities that go to define a competent head - especially if they involve relationships with other people?

We could ask these other people. Most teachers would be able to give a good account of those qualities of their headteacher that go towards motivating and supporting staff. So would the other people who work in schools - secretaries, caretakers and cooks.

It would be argued that these accounts are very subjective. Of course they are - but there is nothing wrong with being subjective. The important question is: how valid would they be? If they were collected systematically with standard sampling techniques and proper concerns for anonymity and confidentiality, then they could be much more valid than more objective measures, such as exam results.

The usual techniques for collecting this kind of data are diaries and questionnaires. There is a case for developing much greater expertise in the construction and interpretation of these instruments, and using them in appraisal systems. One education authority’s guidance manual says that the targets should be directly “attributable to the contribution of the head”. It also says that the criteria should be “objectively measurable” and must not be related to “subjective judgments about an individual’s performance”.

I defy anyone to think of any worthwhile target that at the same time can be attributed to the head’s contribution and objectively measured. Whether or not something is directly attributable is itself almost bound to be a subjective judgment!

We must stop this yah-boo response to objectivity and subjectivity. We must learn to focus much more on the validity of measurements and judgments. We must recognise that the appraisal of a headteacher’s performance is inevitably subjective and we need to concentrate on making that subjectivity well-informed, consistent and rational - in other words professional.

Dennis Fox is vice-chairman of

governors at a Nottinghamshire school, and edits the county’s

newsletter for governors.