Associations between height and certain social factors are known to persist throughout the primary school years. To discover whether the height differences between social groups are increasing or diminishing during this time, heights of 7569 English and Scottish 5 to 10 year olds measured in 1972 and 1973 were examined, together with information about number of siblings, father's social class and father's employment status. With the exception of five year old children of unemployed fathers, any increases in height differentials were no more than would be expected from the dependence of height gain on initial height. No evidence was found of absolute decrease in height differences over one year, for any of the three social factors considered, but children from larger sibships grew more than expected given their starting heights. Thus associations between attained height and social factors in five to ten year old children arise almost entirely before the age of five and do not alter appreciably during the primary school years.