A six-year-old child was independently assessed by three licensed educational (school) psychologists and one interdisciplinary team in the UK. All but one of these practitioners believed their assessment to be the first. The aim was to compare the practice of assessors and their conclusions especially in diagnostic categorisation. The methods of assessment and conclusions of the four resulting reports were compared using thematic analysis. There was agreement about the child's specific learning difficulties, intellectual abilities and need for additional support. However, there were extensive differences in the methods of assessment and notable differences in three sets of conclusions, especially in the use of diagnostic terms: one practitioner identified the child's difficulties as dyslexic in nature, the second one identified them as primarily dyspraxic and the third one reported a "borderline probability of Asperger's Syndrome". The diagnosis, therefore, remained uncertain from initial assessment, exposing inherent overlap between diagnostic categories. The disparities in conclusions are discussed in terms of differing contexts and methods of assessment. The validity of diagnostic categories as discrete is questioned. Even where practitioners describe uncertainty, the use of diagnostic terms may be interpreted unambiguously by other actors. (Contains 3 tables.)