(Background: The purpose of the study was to investigate the development of the mastery of preparatory reading skills in the first school year (0 grade) in a homogenous population. Methods: Tests on letter knowledge, phonemic awareness, rapid word naming and word reading were given to 92 children from a high socio-economic area at the beginning and end of the first school year. Results: Older children performed better than younger children at entry to 0 grade. Although both groups improved, the 6-year-olds still performed significantly better than their younger peers after the first school year in letter knowledge and phoneme awareness. Even with professional day care and similar socio-demographic factors, children at different ages will start school with different levels of preparatory reading skills. Conclusions: Younger pupils need more practice during the school year to raise their preparatory reading skills to the level of their older peers. Standardized reading practice will not sufficiently reduce age-related skill differences during the first year of school for simple tasks such as learning the alphabet.