Social Perception Training (SPT) is a program focused on changing the perceptual and cognitive processes involved in suboptimal social interactions. It is administered with whole class of pupils over ten weeks. No previous studies have evaluated its efficacy. The present study investigated the outcome benefit of the program in 18 primary and secondary classes in a Norwegian municipality (aggregated N = 332), using multiinformant instruments administered in a pre-post research design. Pupils reported on cognitive distortions and the learning environment, parents on social skills and problem behaviour, and teachers on classroom performance. Results indicate overall positive differences, especially for pupils? cognitive distortions. Increased social skills and reduced problem behaviours were also reported, as well as improved peer relations and perceived emotional support from teachers. Overall SPT appears to be a promising and cost-effective intervention program.