Classification is a means of labelling and conceptualizing the data of experience. It serves as a shorthand system, and also as a means of conveying information, enabling us to draw some general conclusions concerning the subject-matter involved. In the field of education and psychology, classification systems are far from precise and represent means of roughly dividing our data into categories. We use these systems to label persons and allocate them to particular groups and have assumed that certain groupings tell us something about the type of education and schooling that individuals require. Thus, we label some as educationally subnormal, others as backward, some visually impaired and others severely mentally retarded. Our educational systems of classification are far from precise and are influenced by an interaction of medical, psychological and social systems of knowledge. A classification system, which is useful to medicine because of implications for treatment and outcome, may be limiting in the hands of other professions wishing to draw different types of inference from the same classification system. If, for example, an individual is described as suffering from Down's Syndrome we not only recognize that he has certain biological abnormalities based on a chromosome aberration but we also believe the diagnosis has various psychological and educational implications, yet the extent to which there is a poor correlation between known chromosomal type and behaviour, and the extent to which there is a13 range of variability in the behaviour of such persons, should modify our use and reliance on such classification procedures.