The main purpose of the study is to estimate the causal effect of preschool on later student achievement. In the current international academic and political discussion, expectations are high that especially preschool education is a promising approach to support students’ literacy acquisition. However, there is little reliable empirical evidence that attending preschool actually affects student achievement on a long-term basis. Limitations often adhere to sample selectivity and omitted variable bias. Therefore, we employ longitudinal trend data from PISA, TIMSS, PIRLS and the Reading Literacy Study and use value-added measures by differences-in-differences analyses. Also, country level analyses allow for controlling different forms of remedial education within countries. Our main finding is that there is no effect of general preschool participation on student achievement.