Background Anxiety constitutes the most common form of psychopathology in childhood and adolescence. Methods This randomised controlled study evaluated the ‘FRIENDS for Life’ school‐based Cognitive Behavioural Therapy programme on overall anxiety, anxiety subtypes and school adjustment. Sixty‐two students aged 12–13 completed measures of anxiety and school adjustment before, immediately after and 4 months after completing the programme. Parents and teachers also rated the students on overall anxiety levels and school adjustment respectively. Results The intervention group's ‘overall anxiety’ and specifically ‘separation anxiety’ reduced significantly during the programme and continued to decrease at the 4‐month follow‐up. Conclusions A significant negative correlation was found between anxiety and school adjustment. The professional implications of these findings are discussed.