In the new “modernised” comprehensive system now taking shape, the aim is that all secondary schools will become specialists. Most headteachers and governors have welcomed this as it offers schools the prospect of additional resources and a clear focus for future development. But, as many have already discovered, preparing a bid for specialist status can be hard work - not least trying to find ways of raising the sponsorship.

So it is often late in the day before would-be specialists face up to the difficult issue of whether or not to select pupils. Some schools might find this an attractive possibility, but need to consider carefully before taking such an important step. Here are some points to think about.

The first point is to work out what kind of selection is allowed by law and what is not. This is not as easy as it might sound. Schools are allowed to select up to 10 per cent of pupils for a specific aptitude in the performance of visual arts, languages, sport or design or information and communications technology. Incidentally, this is open to any secondary school that can demonstrate it has particular facilities or expertise, not just specialists. What they are not allowed to do, according to the 1998 School Standards and Framework Act, is select for ability or general aptitude.

If a neighbouring school, or local education authority, objects to a school’s admission arrangements an adjudicator is called in. Usually the objection is that, while purporting to select by aptitude, the school is actually selecting by ability. So it is crucial we know what the two words mean and the practical difference between them.

Finding a difference between the meaning of two such words is the sort of exercise lexicographers get up to when they haven’t enough to do. Most dictionaries tend to use the two words alongside each other in the definition of both. In an attempt to draw a clear distinction, legislators have also got in on the act. The school admissions code of practice gives the following definition “a pupil with aptitude is one identified as able to benefit from teaching in a specific subject, or who demonstrates a particular capacity to succeed in that subject” - not the most helpful guide to anyone who wants to know what it is.

We can find a way through this by using the word “ability” in the same way as we use “achievement”. Ability is assessed using the normal tests used in schools and elsewhere - GCSEs, musical instrument grades, swimming proficiency certificates. These tests find out what people can do.

The word “aptitude” then means a gift or a talent. It denotes a potential or propensity to develop an ability given appropriate teaching or preparation. In other words aptitude + preparation = future ability.

The next task is to find a means of assessing a specific aptitude that does not trespass into assessing ability or general aptitude. Aptitude tests are hard to come by but there are a few that have been developed for some subjects. There are tests for languages that rely on the propensity of children to recognise the meaning of non-familiar languages. Tests for aptitude in music assess the propensity to recognise pitch, rhythm, harmony and texture. Spatial awareness tests identify aptitude for design and technology. But even these tests have a tendency to select general as well as specific aptitudes. Schools can correct for this by making sure that the pupils selected are spread across the ability range but that is an extra stage to go through.

Aptitude tests for sport are being developed but are not yet established.

There are no aptitude tests yet for the arts. Here it seems reasonable to rely on the assessment of qualified coaches, directors or teachers. But the people appointed to do this must be experienced and independent of the school and the pupils they are assessing. They have to work to published criteria so there is no possibility of discrimination against applicants on the grounds of gender, ethnic origin, disability or family background.

Having done all this, schools must consult their neighbours and parents properly. This does not mean everybody has to agree but proper consultation involves a full dialogue, taking on board reservations that partner schools or parents might have.

If a school gets that far down the selection path there is one further hoop to go through. It has to go back to the beginning and ask itself why it wants to select. From some of the cases we have had referred to adjudicators recently, it seems some excellent schools have found themselves selecting simply because schools around them are doing so. But there is no evidence that they need to select to maintain their standards or ethos or that the children selected do any better than those who are not. There should be a clearly thought-through statement of what the school hopes to achieve by selection and why it is prepared to devote resources and energy to a process that has proved to be both time-consuming and expensive.

Philip Hunter would like to thank Professor Dylan Wiliam of King’s College, London, Tim Oates of the Qualifications and Curriculum Authority, and Chris Whetton of the National Foundation for Educational Research for their advice on this article