AbstractThe aim of this study was to investigate the role of pupil age as a major cause of the birth date effect in scholastic performance. Sex differences in performance were also investigated. A sample of 4123 pupils in Grades III, IV and V was selected from 12 state primary schools in Malta. Since in this educational setting there is only one intake of pupils per scholastic year it ensured that all children within any given year group would have received the same length of formal schooling. Analyses based on a data set consisting of scores in Maltese, English and mathematics derived from the national end‐of‐year examinations showed a strong and consistent age effect in all three attainment measures at each of the three grade levels: the ‘oldest’ pupils performed better in Maltese, English and mathematics than the ‘youngest’ pupils. Results also showed that girls consistently outperformed boys in the three scho