In medicine, it is often possible to specify what is "normal" through the use of carefully controlled clinical trials using large numbers of subjects. Research into some aspects of education can proceed in the same way but there are many areas where the concept of normality is problematic.
Some children with special needs used to be labelled "educationally subnormal", a classification deeply negative in its connotations which often led to inadequate provision. The basis of this classification was the "normal distribution curve", a graphical representation of the range of intelligence among the population.
Subsequent studies called into question the validity of intelligence testing and the reliability of the educational decisions it seemed to justify. In the process, our certainty about what was "normal" began to be challenged.
In other areas, the issue is even more complicated. What, for example, is a "normal curriculum"? It might be possible to reach agreement on the teaching of reading, writing and arithmetic to all children but, beyond that, the territory is highly contested. Some of the choices that young people face are determined by the exigencies of the timetable rather than by any coherent educational rationale.
The consequences can be long-term. A woman in her 40s told me that she wanted to study art in secondary school but her parents and teachers insisted that she take mathematics instead. She has regretted it ever since. Again, who is to say that the informal curriculum followed by some home-educated children is any less fulfilling than the "normal" diet prescribed at school?
Similar issues arise in relation to teaching methods. The teachers we remember from our own schooldays are rarely the conventional ones who followed approved methods in a straightforward way. They are those who dared to be different, who had distinctive approaches to their subject, who had striking characteristics of speech or manner, who possessed humour and enthusiasm, and who did not force all pupils to conform to the same mould.
People who have the opportunity to visit many different schools are often struck by the fact that each one tends to assume that its way of doing things is standard. From within the organisation, rules, rituals and conventions are regarded as "the norm" while, from an outside perspective, they can seem arbitrary or bizarre. The result, particularly where there is a low turnover of staff, is that strange practices can be accorded an authority they do not merit. Once again, the elusiveness of "the normal" becomes apparent.
A final piece of evidence against normality can be adduced from the fact that early teacher training took place in institutions called "Normal Colleges". I am sure many teachers would agree that, even today, teacher education is often experienced as an abnormal process involving tensions between theory and practice, conflicting demands from university tutors and placement schools, and a significant gap between the approved professional rhetoric and the day-to-day reality of life in schools.
These examples lead to a simple conclusion. When the lunatics have taken over the asylum, the only sensible thing to do is to abandon normality and participate in the theatre of the absurd with relish and style.
Walter Humes is professor of education at Aberdeen University with responsibility for the strategic co-ordination of research.