Age Standardisation and Seasonal Effects in Mental Testing

S ummary . It is pointed out that there are two distinct types of age standardisations for tests of school attainment. One is concerned with allowing for differences in age between children tested at the same time, and the other is concerned with allowing for average changes in test scores with time of year. Standardisation procedures do not normally take account of this distinction. It is also shown that there is no increase in attainment scores between April and July among 11‐year‐olds in the last year of primary school. This ‘seasonal’ effect creates further difficulties in providing satisfactory age standardisations and it is suggested that full age‐time standardisations should be carried out by selecting standardising samples over whole age ranges at different times of year.