Background: Bullying has a profound and enduring impact on academic achievement. However, there is a lack of clarity surrounding the specific mechanisms of this relationship. Aims: This study examined the link between bullying at age 9 and Numeracy/Literacy achievement at age 15 to determine if this relationship is partially or fully explained by psychological difficulties at age 13. Sample: Secondary data analysis was completed on waves 1, 2 and 3 of child cohort (Cohort'98) of the Growing Up in Ireland (GUI) study, respectively, at 9 years (N = 8568), 13 years (N = 7527) and 15 years of age (N = 6216). Results: Longitudinal path mediation model was conducted with bullying at age 9 as the predictor, total (emotional and behavioural) difficulties at age 13 as the mediator and Numeracy/Literacy scores at age 15 as outcomes revealing significant indirect effects of bullying on achievement, via psychological difficulties. Conclusions: We discuss the impact of bullying on the student's psychological well-being, the relationship between bullying and academic attainment and how this may be tackled to avoid consequences throughout education and later in life. Educational Impact and Implications: This study emphasizes the need for schools to address the emotional and behavioural difficulties occurring as a result of bullying in order to improve the overall educational experience of aThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.