This paper presents estimates of achievement-related peer effects on school students’ literacy using data from national test scores, across multiple literacy measures and student cohorts, for the population of public secondary school students in Years 7 and 9 (aged 12/13 and 14/15 years) in the Australian state of Victoria. Identification is achieved via individual fixed effects and by distinguishing between secondary school peers who attended the same primary school as the individual and those who did not. Estimates of peer effects are based on the new peers, whose primary school achievement could not have been affected by the individual. The results provide strong evidence for the existence of peer effects, with small but positive and statistically significant effects from having higher-achieving peers on average and from having a higher proportion of very high-achieving peers. Further, it is individuals in the middle of the ability distribution who benefit most from having high achieving peers.