Evidence regarding the effect of early reading instruction on later reading achievement is unusually sparse, given the emphasis often placed on early and intensive reading instruction. Capitalising on international differences in school entry age (SEA), international reading studies may provide such evidence; however, only one quantitative analysis has been conducted that looked at nine-year olds over 17 years ago. Therefore, data from the reading portion of the 2006 Programme for International Student Assessment (PISA) study were re-analysed. The relative reading achievement—as a function of SEA—of 15-year-old students across 55 countries was investigated, controlling for social and economic differences. Results suggested no significant association between reading achievement and SEA. Theoretical explanations for these findings are discussed.