The present study investigated the effectiveness of a cognitive-behavioural therapy (CBT) programme delivered by a school psychologist for children with behavioural difficulties in Singapore elementary school classrooms. It examined the impact of a 12-session, psychoeducational group intervention in helping misbehaving pupils to control their school and home behaviours, maintain peer relationships, and improve self-esteem. Ninety-five pupils, aged between 8- and 12-years-old (M = 10.08, SD = 1.10) were randomly assigned to CBT (experimental) groups and control groups. The CBT groups learned and practised skills in self-monitoring, problem-solving, and self-management. The control groups discussed rule compliance and role-played behaviours that conformed to school rules. CBT groups improved significantly in school and home behaviours, self-control, social skills, and self-esteem compared to control groups. Effect sizes ranged from moderate (0.50) to large (2.94). Gains in self-esteem were maintained at follow-up for experimental groups only. The feasibility of implementing group CBT was discussed in light of competing demands on school psychologists to deliver diverse psychological services to children. (Contains 1 table.)