School victimisation and perpetration rates change in frequency with age. However, findings vary by study, gender, and type of bullying, especially offline and online. We provide a comprehensive analysis of age trends by analysing data from 3 large-scale surveys: Health Behaviour in School-age Children (HBSC), EU Kids Online (EUKO), and Trends in International Mathematics and Science Study (TIMSS). Age trends were classified as U (up), S (same), D (down), P (peak), or V (trough). Findings from HBSC and TIMSS confirm a general D trend for victimisation, especially for boys, with rather more P findings for girls. Findings from HBSC and EUKO confirm mainly P (more girls) or U (more boys) trends for bullying perpetration. For both victimisation and perpetration the gender differences are most marked in the last 2 survey periods of 2013/14 and 2017/18. Age trends online are more varied than online, Cyber victimisation appears to decline less often than general victimisation, but girls more than boys show a P (peak) age trend at 13 years in HBSC data. Findings are discussed in relation to theories about the age changes, and the gender differences in relation to both timing of puberty, and interest in social media sites.